Question: What’s the run-down on today’s Pfizer vaccine news?

Answer:  Pfizer’s vaccine news of this morning– early trial results show the vaccine  to be 90% effective in preventing disease among trial volunteers with no concerning side effects– is very exciting!  90% is MUCH higher than most scientists have been expecting.  If it continues to prove this effective, it will be a vaccine more like childhood immunizations (e.g. MMR) than influenza vaccinations! 
The New York Times had a very informative article on the news this morning, here.  Basically, the Data Safety Monitoring Board met this weekend to assess the trial’s progress based on data from the first set of volunteers to contract COVID-19.  As it turns out, ~90% of the 94 volunteers who contracted COVID-19 were those who were in the placebo group!  This is something to smile about.  BUT, the data are preliminary and things can still change.  All we have right now is the press release; no peer reviewed findings yet!  Furthermore, we still have several additional questions that the ongoing trial will resolve:

• Can vaccinated people be asymptomatically infected and thus able to spread the virus to others (e.g. be carriers)?; 
• Does the vaccine impact disease severity?; 
• What is the duration of protection? 

Background

This vaccine (administered in 2 doses/shots) is a new type of vaccine based on RNA technology.  As described by the NY Times, “It takes genetic material called messenger RNA and injects it into muscle cells, which treat it like instructions for building a protein — a protein found on the surface of the coronavirus. The proteins then stimulate the immune system and are believed to result in long-lasting protection against the virus. Other companies, including Moderna, are also using messenger RNA technology.”  The new vaccine did not receive any development funding from Operation Warp Speed, however, the US placed a purchase order in July for 100 million doses.  Company executives expect to have manufactured enough doses to immunize 15 to 20 million people by the end of the year.  

Timing

The Phase 3 trial is expected to continue until 164 people in the 44,000 person trial have developed Covid-19.  Since COVID is so rampant, achieving this milestone should not be long in As STATNews reported today, “In keeping with guidance from the Food and Drug Administration, the companies will not file for an emergency use authorization to distribute the vaccine until they reach another milestone: when half of the patients in their study have been observed for any safety issues for at least two months following their second dose. Pfizer expects to cross that threshold in the third week of November.” For more on vaccine development, see NY Times Coronavirus Vaccine Tracker (Figure 1).

Figure 1. Vaccine Tracker (from NY Times)