The news on the Pfizer+BioNTech Vaccine is welcome. Here is a brief summary of what it means. The results come from Phase III trials. These trials “began on July 27 and has enrolled 43,538 participants to date, 38,955 of whom have received a second dose of the vaccine candidate as of November 8, 2020.”. Vaccine trials are event-driven. What this means is explained  “The study is a case count, or “event-driven,” study: investigators report the number of cases of COVID-19 disease that occur in those who receive the vaccine candidate and those who receive the placebo. If there are many more COVID-19 cases in the placebo group, as compared to the vaccine group, this is scientific evidence that (the) vaccine candidate is effective in preventing COVID-19 disease.” 


The independent Data Monitoring Committee got permission to perform an interim analysis, and when they did that they had 94 cases. The study has enrolled 43,538 participants so far 38,955 of whom have got a second dose of the vaccine. The splitting of the cases between the vaccinated and placebo arm indicated that 90% of those who received the vaccination were protected. 

The data has not been released yet and it will be carefully examined by experts when that happens.


What can we get from all this?


This is an important finding as it shows that a vaccine can protect against COVID-19  progression to severe disease. Experts point out that these results have followed from steps in the trial process that included non-human primates, which other vaccine candidates also have gone through. As these other vaccines also go through to the final stages, some may be able to prevent symptomatic disease. This is now a reasonable extrapolation. These vaccines, as shown in earlier-stage trial settings, generated what are called ‘neutralizing’ antibodies, which are likely to be effective against disease progression. While evaluating Phase III trial data and vaccine efficacy,  it is of course kept in mind that neutralizing antibodies will also be present in the population due to exposure to the virus. 


We do not know yet (as this could not be measured the way the trial was designed) whether shedding of the virus in those vaccinated was reduced/eliminated. In other words, while the vaccine seems effective at preventing severe disease, does it also reduce transmission? We also need to see the age-stratified protection data to see how well the vaccine protects against severe disease in the most vulnerable. While efficacy can wane over time, the hope is that it will last for a significant time. Even a 50% efficacy at the start will be very valuable in a population, the Pfizer+BioNTech is much better (again, need to look at the details).



There are several other vaccines In Phase III trials and others, including those from India, that will enter Phase III soon. The importance of the Phase III trials is that they establish efficacy by testing several thousands to see how many get infected compared to the placebo arm. The presence of neutralizing antibodies seen in earlier stages is a valuable indication of potential protection, buy the end-points of the Phase III trials can demonstrate that. The Phase III trials also flag rare safety concerns. 


The cold chain requirement of the Pfizer+BioNTech vaccine poses a challenge. It needs to be stored at about -80C through the delivery chain.  The logistics of handling this is a tough but not insurmountable task even for a distributed immunization program. Efforts are also ongoing at a fast pace to see if warmer temperature chains can be made sufficient. Here, keep in mind, while choosing vaccines for large and distributed immunization programs, as distinct from those that are available at a specific site, other vaccines with less stringent requirements are on their way. The likelihood of their success is viewed more favorably now after the results from the Pfizer+BioNTech vaccine. 


The Pfizer+BioNTech vaccine will likely apply for emergency use authorization. In any case, the vaccine will be available soon. 

The pricing and availability of this vaccine will be negotiated through multiple mechanisms which include arrangements with bodies such as COVAX or with individual governments and companies. Balance and clarity will be important in taking this process ahead. The  Pfizer+BioNTech is an important advance, but keep in mind that the rest of the pack is very close by.

In sum, these results from Pfizer+BioNTech opens the closed door to vaccine availability a little. One can legitimately expect more good news from more vaccines and expect that the door will open even more. But, even after this and others are licensed, the available doses will be small at the start. These will have been administered according to priorities that are set. It will take a while till stockpiling and distribution start taking effect on the scale in our large and diverse population. Till then, stay safe, observe all precautions, and protect yourselves and the vulnerable. 

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