The Pfizer and BioNTech vaccine candidate news

The Pfizer and BioNTech vaccine candidate news – what does it all mean?


By Candela Iglesias Chiesa, MPH, PhD 

On Nov 8, Pfizer and BioNTech announced the results from the interim analysis of their Phase 3 trial for their COVID-19 vaccine candidate (with the very difficult name of BNT162b2), showing 90% effectiveness of the vaccine. This is exciting and promising news, but there are caveats. We explain it below.

What the results mean

These interim results show 90% effectiveness, meaning 90% less infections from COVID19 virus in the group of volunteers who were vaccinated compared to the group who received a placebo. The study has enrolled 43,538 volunteers so far, but this is a vaccine that needs 2 doses, and 38,955 of them have received both doses.

The good news

  • Potentially 90% effectiveness. This is much higher than anyone dared to hope for. Most experts were hoping for a 50-60% effectiveness. Even if the final effectiveness is lower than 90%, this is a strong starting point.
  • This is data from a Phase III study – the last and biggest type of clinical trial that a vaccine or drug has to undergo, to prove that it works in a large variety of people (watch our video explaining clinical trials).
  • Diversity: They also report that 42% of their volunteers in the global study and 30% of those in the US arm of the study come from diverse racial and ethnical backgrounds, which is important to make sure that the vaccine works similarly in different populations.
  • Safety: while no safety data was shared, the press release stated that the interim analysis did not report any serious safety concerns.
  • Potential good news to increase hope for other mRNA vaccine candidates being tested. mRNA which uses genetic material from the virus, to cause the body to create a viral protein so the immune system can then recognize the virus and learnsto attack it.

The caveats

  • It’s an INTERIM analysis. We need to await final data. Importantly though, it’s a planned interim analysis (it’s not just that at some point they decided to peek at the data). The study aims to do the final data analysis when 164 cases of COVID19 have happened, while so far only 94 cases have occured across both arms of the study.
  • No trial data has been released yet. What little data we have so far comes from a press release. Meaning that there has not been any peer review. That said, the interim analysis was carried out by an external and independent Data Monitoring Committee.
  • The results evaluate effectiveness starting at 7 days after the second dose of vaccine. Since the study started enrolling at the end of July 2020, the volunteers who have been vaccinated the longest have only been so for 3 months. Thus, its too early to know how long protection from the vaccine will last. That said, data from the previous trials seem to suggest that immunity may not wane too fast.
  • Also, we don’t know yet if the vaccine will prevent severe disease, although the companies will be looking at that.
  • There is no safety data reported yet, although the press release did mention that the Data Monitoring Committee did not raise serious safety concerns. That said, we know from previous trials that the vaccine does cause some side effects in some volunteers.
  • The vaccine needs super cold storage and two doses which makes the logistics of distribution much harder.

While we await with hope the final data, I propose that we toast to all the volunteers who have participated in this trial, as well as to all the healthcare workers and others who have made it possible. It’s a massive effort.

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