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..!

Is Sinovac (and Other Covid Vaccines) Effective Enough?

 Is Sinovac (and Other Covid Vaccines) Effective Enough? & Do We Need Booster Shots FOR DELTA VARIANTS?

We know that the first covid19 vaccines 

were a welcome development during the pandemic because they were the ones that offered hope to an end for this pandemic. But, what we know is that these vaccines would keep us safe and protected against severe disease but there's a lingering question among us as to how long will the production last would variants make these vaccines available to us less effective? 

Another question would be, Would everyone need a booster shot in six months or in a year or in two years so could some people get away without that boost? or it is advisable for all these are actually the same questions that headlined the meeting of the Centers for Disease Control and Prevention Advisory Committee on immunization practices. 

What we know of as of now that the group isn't making recommendations around covid-19 vaccine boosters, but the discussion shows how leading health experts are thinking through these issues. So, let's go through them one by one. 

Here's what we know so far that the vaccines authorized by the World Health Organization (WHO) based on clinical studies work extremely well at protecting the majority of people from coronavirus infection. We know that the protection seems to last a while but, we're not sure quite how long. What we know so far that protection lasts longer than flu vaccination of which we give flu vaccination to our patients with diabetes every year. 

So far, data at present also shows that the shots still work against coronavirus variants even the fast moving delta variant. However, there are special groups of people where the vaccines don't work as much as we want them to work and these include people who are immunocompromised, particularly, people who had organ transplants. These people often don't produce antibodies after regular doses of covid19 vaccines and thereby neuro research have shown that third booster of covid19 vaccine could give more protection to these groups of immunocompromised people. That's the group that CDC seems to think could be the first to get a booster because we have clear signals that it could help these groups of people to protect against covid-19. Then after we learn more about how long the protection lasts for everyone else or if new variants emerge experts could hammer out details about boosters for the rest of us. 

In short at present, there's really no data to support recommendations for booster doses except for the caveat in severely immunocompromised hosts who are not able to mount a strong immune response. For other patients especially the general population, what we know for now is that the data will come later and that ongoing studies are tracking the durability of covid-19 vaccine protection and the CDC is watching to see if any variants evade the vaccine at present. 

Ongoing studies are tracking the durability of covid-19 vaccine production. For example, the CDC is watching to see if any variants invade vaccines and second several studies are present are ongoing  to check if people should get a third dose of the covid19 vaccine that already exists or a new shot with an updated form of the vaccine that targets specific variants. Most experts do agree however that if we start to see an uptick of infections or re-infections for people or new infections in people who have been vaccinated, that's a clue that we need to move quickly. 

Covid-19 vaccines are likely to be rolled out in UK in the fall to avoid another winter surge. Seven different vaccines are being tested in volunteers in England in the world's first booster study. So we have to await the data of booster shots. What we also know is that more transmissible variants including the Beta strain that emerge in South Africa require higher antibody titers to prevent infection. Prompting vaccine makers including Pfizer and Moderna to test whether tweaked versions of their existing shots will provide broader immunity. 

We also have data that one dose of the Novovax variant directed vaccine may provide sufficient protection against these strains in individuals previously immunized with against covid-19. So the modified shot has also the potential to provide broad protection against various strains if used as a primary vaccine regimen and this is one exciting new vaccines that soon will hopefully be rolled out across the world which is Novavax.   

As for SINOVAC, it is the primary vaccine that we're given that has been given to most of the general population. We now know that based on a second phase clinical trial produced by synovac company the third dose of Sinovac's inactivated vaccine can increase antibody response tenfold in a week. The study showed that the volunteers who had received two doses of Sinovac covid-19 vaccine and then received a third shot after three to six months, the antibody response inside the body's soared tenfold in a week and 20 fold in 15 days. It has been shown that after completing the two shots clearly, our body is producing very robust immune memory. 

Sinovac vaccine and the company will however conduct more thorough and longer periods of research to determine the best time to receive the booster for the general public based on the analysis of early vaccinated groups to combat the threat of mutant strains. Data from people vaccinated six months ago is now being analyzed and preliminary results show that antibody levels and about half of them are still good within that specific period. But the general concern at present is not whether to give booster shots or not. 

The CDC is pretty worried about the troubling rates of vaccination in the world. Only 17.7 percent of the world is vaccinated. In fact, if you look closely at the data clearly we have a long way to go in terms of vaccination but there are certain areas in the world like Israel where in majority of the patient population have already been vaccinated. We still have a long way to go to get the population protection. 

We know that unvaccinated people don't need the boosters because they really need their first shots and we need to convince this unvaccinated people to help protect the community by getting their shots having more people vaccinated will definitely slow the spread of the virus and prevent new variants. It will protect people who are immunocompromised too, when everyone around them is far less likely to have covis-19. Therefore, they are at far lower risk of catching it. Figuring out boosters definitely is important but getting unvaccinated people their shots right now is a very critical way to protect everyone prior to going around giving vaccines or giving everyone boosters we really need your help in convincing your friends and your relatives that hopefully they can get their vaccines and we can in general improve the overall vaccination rate.