COVID-19 Vaccines: Types and Mechanisms of Action

Viruses use their spikes to attach themselves to human cells during an infection. It exploits the machinery of the host cell to replicate after entering the cell, creating viral proteins and genetic material. As the host cell dies, they are combined into new virus particles and discharged.

Resultantly, more cells are infected by new virus particles, which destroy body tissues and cause symptoms. Infected cells send out warning signals to the immune system by exhibiting viral protein fragments on their surfaces. By doing so, infected cells are believed to transmit the viral antigen to specific immune cells, such as cytotoxic T-cells, and so activate them. 

At the same time, detritus from dead cells and virus particles are taken up by so-called professional Antigen-Presenting Cells, the most effective of which are dendritic cells.

Dendritic cells patrol the tissues of the body, constantly sampling their surroundings for intruders. Dendritic cells swiftly leave the tissue after capturing the antigen and travel to the next lymph node, where they present the antigen to another type of immune cell known as helper T-cells. B-cells in lymph nodes are also activated by viral particles. 

These immune cell clusters collaborate to mount two types of antiviral immunity: 

1. Cell-mediated immunity 
2. Antibody-mediated immunity 

However, the procedure could take many weeks, during which time the person will be sick and the virus will have damaged a large number of cells.

Vaccines give viral antigens to the immune system without inducing disease. A vaccine-generated immune response is comparable to that induced by a natural infection, albeit some vaccinations may only induce antibody-mediated immunity, making them less effective. Even when there is no infection, the immune system can produce symptoms that resemble a mild infection. For a few days, the lymph nodes near the injection site may become swollen and sore as they begin to produce antibodies. This is proof that the vaccine is working against infection.

Many existing vaccinations contain a virus that has been attenuated or inactivated. Because the entire virus is used in these vaccines, significant safety testing is required. In those with weakened immune systems, attenuated vaccinations may still cause sickness. 

• Only antibody-mediated immunity is induced by inactivated vaccines (Sinovac, Covaxin). 
• Only a portion of the virus, usually a spike protein, is contained in subunit vaccinations (EpiVacCorona). 

Although these vaccinations do not cause disease, they may not be seen as a danger by the immune system and hence fail to elicit the desired immunological response.

As a result, adjuvants are frequently used to encourage antigen-presenting cells to recognize the vaccine. A subunit vaccination could alternatively be made out of empty viral shells that haven't been genetically modified. These vaccines may not require adjuvants to be seen as dangerous because they have the size and structure of a disease, but they are difficult to make.

Instead of the antigen itself, nucleic acid vaccinations contain genetic instructions for generating the viral antigen. Viral DNA is introduced into the nucleus of the cell, where it is translated into mRNA. In the cytoplasm, mRNA is translated into viral spike protein. Like other types of vaccines, the protein is then exhibited on the cell surface.

To reach the cell's nucleus, naked DNA vaccines (Inovio) require a specific delivery technique. Alternatively, a virus that isn't related to the DNA could be utilised to distribute it. The vaccine is also known as a viral-vector vaccine (Sputnik V; Johnson & Johnson's) in this situation. 

The Oxford-AstraZeneca Covid-19 vaccine, for example, uses a chimpanzee's adenovirus as a vector. The coronavirus spike gene is inserted to the adenoviral genome, which has been edited to eliminate viral genes. The viral vector cannot reproduce or cause disease in this manner, but it does serve as a vehicle for delivering the DNA. Because most people have been exposed to human adenovirus and have developed immunity to it, a non-human adenovirus is employed. Immunity may kill the vehicle before the DNA can be delivered, reducing the vaccine's effectiveness.

Concerns about viral DNA integration into the human genome have arisen as a result of DNA vaccinations. However, research in animal models have revealed that the incidence of integration is far lower than that of natural, spontaneous gene changes. 

mRNA vaccines (Pfizer, Moderna) deliver mRNA, which provides the instructions for producing the viral protein. mRNA molecules are transported in a lipid coating that will merge with the cell membrane when it reaches it. The mRNA is translated into viral antigen in the cytoplasm and subsequently presented on the cell surface. mRNA vaccines, unlike DNA vaccinations, are highly unlikely to incorporate into the human genome.  

Apart from all of the information we have so far, we are unable to compare any vaccine to another at this time. Because there is still a lot of research to be done on this subject.

Is Sinovac effective enough?| Which COVID vaccines are most effective?

The CoronaVac vaccine against Covid-19, produced by Chinese pharmaceutical firm SinoVac, has been approved for use in 39 countries around the world—with more than 1 billion doses already distributed. Yet, following a series of Covid-19 deaths among Indonesian healthcare workers that were fully vaccinated with SinoVac, Malaysia will stop using the vaccine, and some have called for Thailand to do the same. So the question is: 

Why are countries rejecting SinoVac? 

This blog will help you to go through the scientific literature to give you everything you need to know about SinoVac’s effectiveness. Specifically, It will help you to know what is known about: 

• How effective SinoVac is at preventing infection, hospitalization, and death? 
• How the effectiveness changes against variants, such as gamma or delta? 
• How quickly immunity drops after vaccination?  
• How SinoVac compares to other vaccines? 

And, as a bonus, here you will find a study that actually ranks vaccines for their effectiveness. Before looking at literature let's know: 

What kind of vaccine is SinoVac? Is it like other Covid  vaccines? 

SinoVac’s CoronaVac vaccine is an inactivated virus. This is the most conventional type of vaccine, using the same technology as the polio vaccine in the 1950s. 

Essentially, live SARS-CoV-2 virus was collected from infected patients in China at the beginning of the outbreak. Then, the virus was mass produced in monkey kidney cells, extracted, then treated with chemicals to inactivate it, rendering the virus unable to reproduce. 

This is different from almost all other Covid vaccines, including the mRNA vaccines from Pfizer and Moderna, as well as the viral vector vaccines from Astra Zeneca, Sputnik, and Johnson & Johnson, which all stimulate the in vivo production of viral spike proteins. Only Sinopharm and the Indian Bharat vaccines use the inactivated virus approach that is found in SinoVac.

So, does it work? & How is vaccine effectiveness actually measured?

Vaccine effectiveness cannot be determined from observed trends, like for example, if infections or hospitalizations drop in a city or country once a vaccine is administered in the population. That trend tells us nothing about the vaccine. This is because there is no way to isolate what factor caused that decline to occur—it may have been the vaccine, or it may have been several other factors unrelated to the vaccine. 

Instead, a study design needs to be able to measure both an outcome and a factor in each individual. The outcome is usually infection or hospitalization or death, and the factor would be whether that person has had a vaccine. The most reliable way to do this is with Phase 3 clinical trials—a type of study called a randomized placebo-controlled trial, where participants are randomly assigned into vaccine or placebo groups. 

However, effectiveness can also be determined outside of trials using real-world data through two other study types: retrospective test-negative case-control studies and prospective cohort studies. We’ll be looking at data on SinoVac from all three of these study designs.

So, let’s get into it.

SinoVac had Phase 3 trials registered in Brazil, Chile, Indonesia, and Turkey. However, only data out of Turkey was used in the phase 3 trial publication, which came out in The Lancet on July 8, 2021. 

The analysis included 10,029 participants, with 2/3 assigned to the vaccine and 1/3 assigned to a placebo. The results found that the vaccine was 83.5% effective at preventing symptomatic infection among fully vaccinated people. This number places it in the middle of vaccines for effectiveness based on phase 3 trial data alone. 

So, SinoVac reports a relatively high vaccine effectiveness from this phase 3 trial, but it’s based on a fairly narrow set of data. 

For a clearer answer, we need to look at studies with more data. 

A much better study comes out of Chile. It’s a cohort study, which means it looked at an entire population of people in this case, every adult in the national public health insurance program of Chile, which ultimately included data on 10.2 million people covering 3 months from February 2nd to May 1st, 2021. 

In that time, more than 4 million people received a SinoVac vaccine. And, overall, more than 218,000 people in the cohort got Covid-19, resulting in over 22,000 hospitalizations and 4000 deaths. 

So with this much richer dataset, what did they find? 

Among people fully vaccinated with SinoVac, they estimate the vaccine was: 

• 65.9% effective for preventing Covid-19, 
• 87.5% effective for preventing hospitalization, and 
• 86.3% effective for preventing death from Covid. 

So, with a much larger dataset we see that SinoVac’s actual vaccine effectiveness is probably about 66% for preventing symptomatic illness—a much lower number than the 83% reported from its published phase 3 trial. 

But could any of these difference be due to differences in variants? 

Other vaccines, including AstraZeneca and Pfizer, have reduced effectiveness among the variants alpha, beta, gamma, and delta. However, no such study has directly compared the effectiveness of SinoVac among different variants as of August. 

What we can do, however, is look at genomic sequencing data to see what variants were spreading throughout each study. For example, the phase 3 study in Turkey covered the period from September 2020 to March 2021.

Looking at genomic sequencing data out of Turkey, we see that D614G was circulating. This form of the virus predates Alpha, Beta, and all other variants and is close to the original wild-type virus out of Wuhan. 

On the other hand, the cohort study from Chile took place from February to May 2021. There, Lambda and Gamma were widely circulating. Using this information, we can see that variants may partly explain differences in the effectiveness estimates seen between Turkey and Chile. And, one more study out of Brazil shows how SinoVac did against Gamma.

In the study, which looked at the elderly in Sao Paolo, effectiveness of SinoVac against Gamma was: 

• 46.8% for infection, 
• 55.5% for hospitalization, and 
• 61.2% against death.

What we see is that SinoVac’s effectiveness against all outcomes drops with older age and with more virus mutations. 

But what about Delta? 

Researchers in Thailand collected blood samples from healthcare workers who had been fully vaccinated with SinoVac and then tested to see if antibodies in that blood could neutralize the virus, looking at the original viral strain, known as wild-type, and also with the variants alpha, beta, and delta. What they found was that antibodies from people vaccinated with SinoVac were very good at neutralizing wild-type SARS-CoV-2—able to do it about 98% of the time. 

This makes sense, since SinoVac is just an inactivated form of the wild-type virus. However, against alpha and beta, that neutralization rate dropped to 75 and 70%. Against, Delta, SinoVac antibodies could only neutralize the virus 48% of the time. So, SinoVac’s effectiveness is reduced against the current variants. 

But what about waning immunity in our bodies over time?

We know already that immunity requires time to develop. Even after receiving a full vaccine dose, the full immune response generally develops about two weeks later. 

But, what about after that? Once immunity does develop, how long does it last?

Researchers in both Brazil and China have shown that SinoVac’s antibody levels drop quickly. In Brazil, researchers looked at 133 healthcare workers that received two full doses of SinoVac and collected blood samples from them starting on the day of the first dose, then again at days 10, 20, 40, 60, and 110 days after the first dose. Then they measured levels of antibodies against SARS-CoV-2 proteins. After the first dose, virtually no antibodies developed. Then, about two weeks after the second dose, so 40 days after the first dose, antibodies peaked. Then, they steadily dropped. Antibody levels dropped in half about every 1 to 2 months. Even data from SinoVac itself confirms this drop. They found that after 6 months only 18% of people had neutralizing antibody levels considered sufficient for protection.

Now, the immune system has other tools beyond neutralizing antibodies, so this doesn’t mean a person’s immune system is completely helpless 6 months after vaccination with SinoVac. But, a major study in the journal ''Nature'' shows that neutralizing antibody levels are highly predictive of immune protection. 

So with that in mind, let’s rank the vaccines. Looking strictly at phase 3 trial data, SinoVac might appear to be somewhere in the middle of the pack among Covid vaccines. 

So who’s number one? 

According to the study, Moderna is the most effective Covid vaccine. Next is Novavax. Third is Pfizer. And fourth is Sputnik. Then, we start to drop down to the next tier of vaccines. At 5 we have Astra Zeneca. Behind that is Johnson & Johnson. And, coming in last is SinoVac.

So, what does all this mean? 

Because SinoVac has the lowest levels of neutralizing antibodies among widely used Covid vaccines, it is not an effective tool for creating herd immunity or preventing the spread of the coronavirus. That said, a SinoVac vaccine is still better than no vaccine when it comes to reducing risk of death and severe disease—at least for a short window of time. 

However, compared to other Covid vaccines, SinoVac and its cousin Sinopharm, are less effective at preventing death, especially against current variants like Delta. Thus, the logical policy would be to seek better alternatives—just like Malaysia has already done. 

However, experience thus far has shown that decisions to approve vaccines seem to be motivated more by geopolitical and financial interests, rather than on scientific data. Therefore, it’s up to citizens to keep pressure on their government officials to ensure transparency in vaccine agreements. One tool is the UNICEF vaccine market dashboard, which can be used to track vaccine agreements across the world.

The Delta Variant: Everything You Need to Know..!

Are you ready for some COVID news? Yeah, I know, me neither. But I wanted to talk about something that’s been in the news, and that you may even have questions about: the Delta variant. 

So in this post, we’re going to talk about what it is, why it’s here, and what you need to know.

The Delta variant is a strain of the SARS-CoV-2 virus, which is the virus that causes COVID-19. It’s one of several variants that’s acting unique enough to qualify as a distinct strain. Those get Greek letters for names right now, like Beta and Gamma, plus the first dominant strain: Alpha.

Since it was identified in late 2020, it’s quickly becoming the dominant strain in many parts of the world. That includes countries that had successfully managed earlier strains and relaxed public health measures, like the United States and France. And what makes this variant worrisome is that it looks like it’s more easily transmissible than previously dominant strains. 

The World Health Organization (WHO) says that the Delta variant is the most transmissible of the variants identified so far. We don’t yet know why it’s able to spread so much more readily, though.

One study has proposed that it’s because infected people have higher viral loads, that is, more copies of the virus in their bodies. If true, that would mean that the Delta variant reproduces faster and is more infectious at early stages than other dominant variants. This variant may also affect our bodies differently than previous dominant versions of the virus. 

The study I mentioned also suggested high viral loads may be related to a shorter incubation time, meaning infected people show symptoms faster. However, this paper has not yet been published or passed through peer review, so we’ll need further confirmation. 

Other data indicates that the Delta variant’s symptoms might be slightly different, with headaches, fever, sore throat, and runny nose being common while cough and loss of sense of smell aren’t. It also comes with some new symptoms, including hearing loss.

But are those infections more severe?

Well we’re not sure yet..!

Some experts say that may be likely, and there are some reports that the Delta variant may be more likely to lead to severe illness compared to other strains. And a report from Scotland suggests hospitalization for unvaccinated individuals is twice as likely if the patient is infected with the Delta instead of Alpha variant. It might be that the Delta variant is more dangerous. Or that it’s spreading faster through more vulnerable populations. And easing up of public health measures has certainly played a role as well.

The situation in India seems to have been a perfect storm. Their vaccination campaign was just starting to get going. Officials had relaxed restrictions on large public gatherings, and that plus the heightened transmissibility may have let the Delta variant spread through the population rapidly. 

But it’s not a simple matter of India relaxing social distancing and other public health measures. Because here’s where we run into another wrinkle: In Australia, most of their public health measures, like contact tracing and social distancing, have been seen as a model worldwide. And the Delta variant has punched right through them. Relatively speaking, anyway. 

For most of 2021, Australia has managed under 100 new cases a week, but since July, that number has skyrocketed to around 2000 a week. That’s still low compared to some countries, but it’s pretty troubling. What Australia hasn’t had, so far, is a high vaccination rate. But even vaccinated individuals may need to be wary.

There’s been a lot of attention paid to so-called breakthrough infections, which is where someone who has been fully vaccinated still gets sick. There have been a few well-documented outbreaks that included a substantial number of vaccinated people. Now, it’s worth noting that some breakthrough cases are expected. No vaccine is ever perfectly effective at preventing infection. It’s worth the reminder that most of the vaccines in use right now were first tested around their ability to prevent severe disease, not necessarily stop transmission.

Data from the World Health Organization suggests that a number of vaccines, including Moderna, AstraZeneca, and SinoVac, have so far been over 80% effective against severe disease, hospitalization, and death. 

So the question becomes whether the Delta variant is more likely than others to infect vaccinated people. And whether those people would go on to spread it. We didn’t have much data concerning vaccines and the Delta variant, but we have some. 

A paper published in July in the New England Journal of Medicine suggested that two doses of both AstraZeneca and BioNTech-Pfizer’s vaccines are effective against the Delta variant. They lost only a few percentage points of efficacy compared to an older strain. Now, both of those vaccines are administered in two doses. And the paper did find that only a single dose of either was less effective against the Delta variant, dropping from about 50% to only about 30%. That seems to be the case for other variants as well. Altogether, it is possible for someone who is fully vaccinated to be infected with any variant. 

According to the CDC and some pre-print data, people with breakthrough infections of the Delta variant may have a viral load just as high as someone who isn’t vaccinated. And remember, the Delta variant might come with a lot. This has raised concerns about how much vaccinated people might still spread the infection. Though it’s worth noting that high viral load isn’t necessarily an indication of heightened infectiousness. It could be that those viral particles are present in the body, but have been deactivated by the immune system. So they’re not actually a problem. And as more people get vaccinated, the proportion of breakthrough cases to normal cases will rise, because the proportion of vaccinated people to unvaccinated people will rise, and you can’t have a breakthrough case unless you’re vaccinated. That’s what it is.

So, what can we do?

Well, we don’t yet have a lot of concrete answers regarding the Delta variant. But remember that vaccines still seem to work. And by “work”, here, I mean they help limit severe illness, hospitalization, and death even if people do get sick. 

Some of the vaccine manufacturers are looking into booster shots, but many public health experts say they would rather focus on getting to people who haven’t yet had an opportunity to get even a first dose. And this isn't just a question of logistics, but equity, as most of the available vaccines have gone to rich countries so far, leaving many vulnerable populations waiting. 

We still do have all the stuff we had at the start of the pandemic. I’m talking about you’re quarantining if you’re feeling sick, you’re washing your hands, all that good stuff. These will continue to be an important part of limiting spread as much as possible. We can see from Australia’s example that social safety interventions like distancing aren’t bulletproof. But vaccines, in the absence of those same measures, aren’t enough either, because breakthrough infections happen, and a lot of people remain unvaccinated. It’s going to take a comprehensive strategy to stay ahead of this thing. 

Meanwhile, experts are keeping an eye on this and other variants, like Lambda, which also appears to be more infectious and possibly resistant to vaccines. Unfortunately, even though we all really, really would love to believe otherwise, COVID isn’t over yet.

Thanks for reading this post. 

I hope it brought a little clarity to the confusing ongoing situation we find ourselves living in...!

STAY SAFE AND FOLLOW PRECAUTIONS..!

Biomanufacturing a COVID-19 vector vaccine |ASTRAZENECA

Approaches to vaccine development to prime the body's immune response to COVID-19 include; 

• Using weakened viruses,
• Using viral proteins, 
• Using specific viral genetic code, either DNA or RNA, directly or creating viral vectors with specific viral genetic code. 

A COVID-19 adenoviral vector vaccine is an adenovirus vector based on a common cold that has been modified and inserted with the genetic material for the SARS-COV2 spike protein. 

Production starts with assembly of its genetic code. The adenovirus vector is engineered from adenovirus DNA by removing essential genes to stop it being able to replicate, so it can only act as a carrier and not cause disease. 

Adding the coronavirus spike protein DNA creates the full genetic sequence for the adenoviral vector vaccine. The genetic code is introduced into a producer cell, where it is transcribed and translated to form the COVID-19 adenoviral vector vaccine. 

The human cell line is engineered to contain the missing adenovirus genes so that when the vector vaccine is introduced, it can infect the cells and use the cell machinery and missing viral genes to be able to replicate producing identical copies.

Vaccine molecules are also replicated with the division of the cells and the process continues until the right concentration is reached. 

The addition of a chemical lyses the cells bursting them open and the vector vaccine is harvested ready to be further tested filtered and purified before being filled into vials.

Delta Variant and Vaccines

At least in the United States, the delta variant has popped up and that's what we're going to talk about. But even more importantly, let's talk about variants in general. So if you've got a coronavirus and specifically the SARS-CoV-2 virus and it  goes to infect an individual, the issue is as we've talked about before the virus is going to hijack  your cells to produce many more copies of itself. 

In fact, in some studies it's been shown that the  virus will make up to a billion copies of itself in just one individual, but here's the problem: the  way that it does it is not very accurate and so there will be some slight mistakes, and you might  see a variant being produced in these infections.  

Now, variants are produced all the time; in fact, the  truth is is that most of these variants are just duds. They don't infect anything or they might  not affect as well, but every now and then you might get a mutation that allows the virus to bind  better to the next individual, and that would be a variant of concern which are not very common. We  have some examples we have the UK variant, for instance, or the South African variant. And more  recently, we have the delta variant, which we're going to talk about now. This was first discovered  in India; this should not be very surprising, as you may recall at one point in India they were  getting as many as 400,000 cases on a daily basis.  

Now imagine those 400,000 cases each producing  over a billion copies, 

and you can see there that  it's only a matter of time before you get  a mutation that is fortuitous for the virus,  and you can see here very easily that a mutation that allows the virus to infect better and be more contagious is going to be a virus that is  certainly going to take over the world. In terms of the different types of variants, so while there  may be many different variants at once if there is a variant that is able to infect better. And  that's really all that matters to the virus, is to spread its genetic material as far and  wide as it possibly can. That is the virus variant that is going to win in terms  of the prevalence in the population, and again this mutation that causes increased  fitness can be manifested as better binding or evading the immune system. There's a  number of different ways that this can happen, so as it turns out, this delta variant has  some characteristics of it and it's known as B.1.617.2. It seems that it is more  contagious than the original virus to give you an example. 

Some experts have said that if you look at the original virus,the number of people that one person would  have infected otherwise, known as the R-naught (R0), it was originally around 2.5. This delta variant has been estimated anywhere between 3.5 and 4.0. Okay, so it seems to be more contagious, but  

where does it seem to be found the most?

Well, there was another paper that was  published. This paper was known as the "REACT-1  

round 12 report," and while it has not been  published or peer-reviewed as yet, there are some interesting findings. This was put out by the  Imperial College in London in the United Kingdom, and what they found is that the prevalence of the  delta variant in those aged 5 to 49, in other words, those people less than 50 years of age, was two and  a half times higher compared to those that were age 50 years and above. And so while it is possible  that people over the age of 50 are more likely to be vaccinated, there could also be a connection  between this virus and younger aged individuals. All right, what about hospitalization? Well,  there was a correspondence that was published in the Lancet regarding the delta variant, and they  were able to look at PCR, and what they found was surprising. What they found, essentially using  a Cox regression analysis, which is a way of adjusting for age, sex, and economic status, temporal  trend comorbidities, was that the delta variant had a 1.85 times higher risk of getting the person  infected in the hospital with severe COVID-19. So if you look at the SARS-CoV-2 infection since  April in the United States, you'll see here that the British variant, or the UK variant, the B.117, has  been up to this point the most dominant infection. But as of recently, there is one that is taking  over very quickly, and that is the delta variant. And as you can see, the delta variant has made some  inroads very quickly here in the last two to three months. And the reason for that is because it is  the most infectious variant that is currently there in the UK, where greater than ninety percent  of the cases are the delta variant. It is what is fueling the latest surge.

 At least 60 percent of  the population is vaccinated with two doses, which is actually very good, and despite the fact that  the cases have gone up in England and in Wales, Scotland and Northern Ireland, the good news is  that the corresponding deaths have not come along with that surge as yet. In Israel, where they've  done a tremendous job of vaccinating, primarily with the very effective Pfizer-BioNTech vaccine,  there has been only a small recurrence of cases, at this date, most of them from the delta variant.  So where we stand here in the United States is that there has definitely been a resurgence and a  doubling of the number of cases, which is an early sign that there's something potentially coming,  and we are seeing here on the daily deaths chart that for the first time, daily deaths have stopped  going down and are now starting to creep up.

In California, and specifically in Southern  California, where I practice, there has been a 

recent resurgence of cases of SARS-CoV-2. Daily  deaths have not yet picked up, but I can tell you anecdotally, in the hospitals that I work at and  in the friends that I have, some of them in LA County, there has been an increase in the number of  admitted cases. For instance, one hospital where I work at had not seen COVID-19 patients in months,  literally, are now admitting patients with COVID-19 and some of them are requiring high levels of  oxygen. So given that, what are the tools that we have? How well equipped are we with the different  vaccines that are available against this delta variant? Let's review the data up to this point.

Now we know that there are several different types of vaccines in the world. We're going to  talk about these four mainly, because we have recent data that shows the efficacy of these  vaccines against the delta variant: that is the Pfizer-BioNTech vaccine, the Moderna vaccine, the  Oxford-Astrazeneca vaccine and the Johnson & Johnson vaccine, and they are different. The Pfizer-BioNTech  and Moderna, of course, are messenger RNA vaccines, and the Oxford-AstraZeneca and the Johnson and  Johnson are DNA that use adenovirus as the vector. And if you have more questions about that,  look at our previous MedCram videos on those particular vaccines for more information  about how they work. Now, as you know, these three first vaccines are first and second shot, and  the Johnson & Johnson vaccine is a one-time shot. Now, there's two different categories that I want to  refer you to, and the first category that we're going to talk about is infection. So infection,  what I mean by that is: does the vaccine prevent the individual from being infected, and therefore  prevent them from spreading it onto somebody else? That has great epidemiological importance in terms  of stopping that R-naught (R0) number and preventing the infection from spreading epidemiologically,  And, of course, who wants to get sick? Nobody does. But there's another important endpoint as well, and  that's hospitalization. Does the vaccine prevent the most serious complications of getting SARS-CoV-2, which is of course COVID-19, hospitalization?  

High flow oxygen and ventilation, ARDS, things  of that nature, and so those are going to be 

two different numbers. So let's talk first  of all about the Pfizer-BioNTech vaccine. Now, I'm going to be referencing a number of  articles. Some of them have not been peer-reviewed, but it is recent data. I will give a link to  all of these studies in the description below. So there was a UK study that showed after the  first dose -- so we're talking about usually two weeks after the first dose -- the Pfizer-BioNTech  vaccine, regarding the delta variant, I'm talking about the delta variant now, specifically was 33  percent effective after the first dose and 88 percent effective after the second dose at preventing  symptomatic infection, and that was the UK study.  

Now there was a Canadian study that  came up with slightly different numbers 

that was 56 percent after the first dose and 87 percent  after the second dose. There was an Israeli study that showed after the second dose, they got 64 percent, and there was a Scottish study that showed 79 percent. Now all of these are above 50 percent and would have been  approved if this were the original virus, so I think these are all very good numbers. And again,  we're talking about infection. Now, remember that the primary way that your body prevents infection  is antibodies, and we know that the mutation that has caused this variant may be slightly off  enough that some people's antibody responses may not be good enough at preventing infection, but  remember that one of the things that helps you prevent getting worse is T cell activation. When T  cells are replicated in the human body, they also are replicated in a way that is not perfect, so it  allows for variance in the T cells, and so if you have variants in the virus and variants in the  T cells, that will sometimes allow for a bit of change. The T cells can be effective at reducing  hospitalizations and taking care of cells that are already infected, and therefore what we  typically find is that the hospitalization numbers are usually much better. So that same UK  study found that after the second dose, there was a 96 percent prevention of hospitalization and death if you  got the Pfizer-BioNTech vaccine after the second dose. And when I say prevent here, I'm talking  about efficacy. So, in other words, if there's a 90 percent plus efficacy, that would be in comparison  to a control, or where there's no vaccine, which would have a zero percent efficacy. There was a  Canadian study that looked after the first dose, there was a 78 percent reduction in hospitalization  after the Pfizer-BioNTech vaccination, and that was the Canadian study. You might be wondering why we  don't have data after the second dose. There wasn't enough data points to make that available in  the study so far. 

There was also an Israeli study that showed in terms of preventing hospitalization  after the second dose that it was 93 percent effective at preventing hospitalization and death  in Israel. So the bottom line here for the Pfizer- BioNTech vaccine is that, despite the fact that  delta is more infectious and causes potentially more hospitalization, Pfizer is exceptionally good  at preventing hospitalization and death from the  delta variant. What about Moderna? Well, there was  a Canadian study that showed that after the first dose, there was a 72 percent reduction, and that  was the Canadian study. In that same study, after the first dose, the Moderna vaccine was 96 percent effective  at preventing hospitalization and death. 

Now the Oxford-AstraZeneca vaccine, which has been given  authorization in the UK. After the first dose, they found it to be 33 percent effective at preventing  infection. And after the second dose, 60 percent effective. That was the UK study. In Canada, where  it's approved, they found that after the first dose, it was 67 percent effective at preventing infection,  and that in Scotland, after the second dose, it was again 60 percent effective at preventing infection.  Now what about hospitalization? 

Well in that UK study, they found that it was 93 percent effective after  the second dose, preventing hospitalization. In the Canadian study that they looked at, it was 88 percent effective at preventing hospitalization and death, if you took the Oxford-AstraZeneca vaccination. So  again, very good numbers at preventing the worst outcomes. Now what about the Johnson & Johnson  vaccine? That's a one-time shot. What they found is we don't have studies, currently, that look at  the efficacy, but we do have some surrogates that could be very informative. Now, the Johnson & Johnson  vaccine was tested against the most strenuous variant, or the worst variant at the time, back  about six months ago, and that was the South  African variant, and when they tested the antibody  response of the delta variant in comparison to the South African variant, what it showed was that  there was a higher level of antibody response to the delta variant than there was even to  the South African variant. In other words, a very  good antibody response to the delta variant.  

You may recall the South African variant with respect to the Johnson & Johnson vaccine, there  were no people who were hospitalized or died of the South African variant 49 days after  they received the Johnson & Johnson vaccine. In fact, Johnson & Johnson put out a statement  saying that as time went on, the immunity got better up to even eight months after the Johnson & Johnson vaccination. So because these vaccinations are so good at preventing hospitalization and  death and also reasonable at preventing infection, your risk from the delta variant is going to be  predicated on a couple of things: number one, it's going to be predicated on whether or not you're  vaccinated. So it's also going to be predicated on the amount of people in your area that  are vaccinated. If there's a high frequency of vaccination in the population around you,  then you're going to be more protected and, of course, the question also is how prevalent  is the delta variant in your community as well? 

I highly recommend going to the CDC covid data tracker, which gives you up-to-date  information in your county and also your state. There are a number of  factors that could be in play: there is  a change in humidity; there is the change in daylight hours; vitamin d production; being  indoors versus outdoors. All of these may play a role in the resurgence of a potential delta  wave.

 I'd like for all of you out there to remain safe, get plenty of sleep, boost your immune system.