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.

Booster Shots? Are they necessary for COVID?

At the moment a lot of countries have high vaccination rates, but there are questions being asked about whether the third doses -known as BOOSTER SHOTS may be necessary, but of course as with much to do with COVID the evidence is still emerging. 

What are BOOSTER SHOTS?

Well, the vaccines we have all do a pretty good job of introducing our bodies to certain diseases and convincing our  immune systems to take that threat seriously. But for some diseases, it takes extra convincing. Which is why you might need to get the same shot more than once -weeks or even years later.

Vaccines teach our immune systems to recognize  certain pathogens, or disease-causing agents. In a nutshell, they trigger the formation  of specialized cells and antibodies that recognize the distinctive proteins that  stick out of pathogens -called antigens. If something with one of those antigens shows  its face, the antibodies latch on and disable it,  while those specialized cells  help to kick it to the curb.

Now, there are a few vaccines that  require multiple doses of the same shot. And there are almost as many reasons  for that as there are different vaccines. Because how much immunity you get from a single  shot, and how long it lasts, can really vary.

Are Booster shots necessary for COVID?

The short answer is, IT'S UNCLEAR.! 

We do know, and this is very early evidence, that antibody levels tend to fall in the weeks and months following a second shot. And this is obviously complicated by the highly infectious Delta variant. But what's important to remember is that antibody levels aren't the only part of our immune system that help give us protection. So we have other, sort of, immune system soldiers like B-cells and T-cells, that all together help provide that protection. 

At the moment, scientists don't quite know what level of antibodies, what level of B-cells and T-cells are necessary to give us that protection that we're looking for. So just because the antibody levels may be falling, that does not mean that our bodies won't remember how to deal with this enemy if we come across it in the weeks and months following the second shot. 

In the UK, for instance, we do have data that suggests that antibody levels are falling in fully vaccinated people in the weeks and months after their second dose. 

However, it does not appear to have directly translated into higher hospitalizations and deaths in in that category of people. Of course the argument for people who are you know compromised or are classed test clinically vulnerable is far stronger, and that's because after getting two shots, they don't get the optimum level of protection as the rest of us do, and so it does make sense to top up that already, sort of, lower level of protection that this category of people may have gotten post their first two shots. 

Overall, though, whether we’ll need booster shots down the line depends on a few things, like how much our immunity declines.  

Does a booster shot need to be the same as my vaccine?

No, not necessarily, and that's pretty much what scientists are trying to figure out. 

The general prevailing hypothesis is that given the different vaccines teach the immune system to recognize the enemy in this case the virus in different ways, if you provide different doses of the different vaccines, that might potentially lead to a more diverse, broader sort of immunity. 

But much like everything else, the science is still ongoing, and we don't really have a  good answer for this yet. 

On the safety side, there are worries, and early evidence from the UK suggests that mixing and matching the jabs does tend to increase the rate of side effects, and so that is something that policy makers will have to contend with. 

In short, we’re going to need a lot more  information before we know exactly how often we’re going to need to be vaccinated against COVID-19 and how much those vaccines will need to change.

The good news is, scientists are on the  case. Immunology is complicated, But we’re getting better against COVID-19.

STAY SAFE AND FOLLOW PRECAUTION.

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..!

Delta Variant is Different - It's the NEW COVID

The delta variant is almost like a whole new COVID virus as it behaves very differently from the previous COVID strains. It has at  least three mutations on its spike protein and more specifically on its receptor binding  domain- that's the part of the spike protein that binds to the ACE2 receptor on the cells in  your body. The delta variant mutations help it bind more efficiently to the ACE2 receptor and  also allows the virus to enter the cell easier.  Also its mutations allow it to better evade the  body's immune system.  

The delta variant  is estimated to be at least 60 percent more  transmissible. One CDC document suggests the delta  variant is about as transmissible as chickenpox with each infected person infecting on average  eight or nine other people. Now compare that to the original strain of COVID which was about as  contagious as the common cold with each infected person infecting two others on average. 

Studies on people infected with delta variant showed that the fully vaccinated had as much virus in their bodies as unvaccinated people did. That doesn't mean worse infection though if you're vaccinated but the significance of having those higher viral loads is going to mean higher transmission of the virus either vaccinated or not even if they don't have symptoms. It's why the  CDC says that even vaccinated people should wear masks in areas of sustained or high transmission.  

Also a study in CHINA found that viral loads of people infected with delta were 1000 times higher compared to people infected at the very beginning of the pandemic and delta transmits in four days compared to six days when you compare that to the original strain. Now there are three somewhat older studies from CANADA, SINGAPORE and SCOTLAND showing that people infected with a delta variant  are more likely to end up in the hospital. So, 

Does the delta variant make unvaccinated people more  prone to dying compared to the original strain? 

Hard to know since there are currently no studies showing that one way or another. It's also trickier to answer this question because you're comparing apples to oranges. You're not only comparing different strains but with the  original strain, no one was vaccinated in 2020 also in the beginning of the pandemic we weren't using things like dexamethasone and tocilizumab, two drugs that we now use to treat COVID because we know that they reduce mortality. With the mRNA vaccines we have Pfizer and Moderna, they're about 95% effective at preventing serious COVID illness. So, we know that even before the delta variant emerged, they're going to be breakthrough cases. 

As compared to original strain, with the delta variant things are looking different. Recently more patients are admitted in the ICU who have chosen not to get vaccinated in their 30s, in their 40s, their 50s. Most of them were otherwise healthy,  all of them not vaccinated. 

The only true medical  exception to not getting the vaccine is; if you've  had a severe allergic or immunological reaction to any of the components of the vaccine like  polyethylene glycol outside of that. We know that it's very safe and very effective in the key to getting past COVID, it's only a matter of time before a new variant emerges that will render our current vaccines useless. So until we reach herd immunity, we'll be in an ongoing battle of  updating the vaccines to fight the new variants.

‘Dangerous period of the pandemic’: WHO warns over Delta variant mutation | COVID

Variants like Delta, which is quickly becoming the dominant strain in many countries, we're in a very dangerous period of this pandemic. 

Many small island developing states have succeeded in preventing widespread transmission of COVID 19 in their communities. But the pandemic has hit you hard in other ways such as declining revenues from tourism, which is affecting your economy significantly. Compounded by more transmissible variants like DELTA, which is quickly becoming the dominant strain in many countries we're in a very dangerous period of this pandemic. 

In those countries with low vaccination coverage terrible scenes of hospitals overflowing are again becoming the known. But no country on earth is out of the woods yet. The DELTA variant is dangerous and is continuing to evolve and mutate which requires constant evaluation and careful adjustment of the public health response. 

DELTA has been detected in at least 98 countries and is spreading quickly in countries with low and high vaccination coverage. There are essentially two ways for countries to push back against new surges; 

1- public health and social measures like strong surveillance. strategic testing. early case detection, isolation, and clinical care remain critical.  As well as masking, physical distance, avoiding crowded places, and keeping indoor areas well ventilated are the basis for the response.

2- And second, the world must equitably share protective gear, oxygen tests treatments, and vaccines. 

WHO have urged leaders across the world to work together to ensure that by this time next year 70 percent of all people in every country are vaccinated. This is the best way to slow the pandemic, save lives, drive a truly global economic recovery, and along the way prevent further dangerous variants from getting the upper hand. 

By the end of this September, WHO is calling on leaders to vaccinate at least 10 percent of people in all countries. This would protect health workers and those at most risk effectively ending the acute stage of the pandemic and saving a lot of lives. It's a challenge, but we know it's possible because already three billion vaccines have been distributed. It is within the collective power of a few countries to step up and ensure that vaccines are shared. Manufacturing is increased and that the funds are in places, in place to purchase the tools needed.