How to spot good Covid-19 vaccine trials results when you see them

How to spot good results from Covid-19 vaccine trials - STAT It doesn't take an epidemiologist to evaluate vaccine trial results. Answers to just a handful of questions can help anyone do this. Patrick Skerrett STAT

Mass vaccination will give us the most promising path out of the pandemic — but only if people trust the results enough to get the vaccine. A well-informed public is among the most crucial elements of a successful vaccination program.

It doesn’t take an epidemiologist to thoughtfully evaluate vaccine trial results. Answers to just a handful of questions can help anyone compare their strengths and weaknesses, distinguish the promising from the inadequate, and know when more information is needed to figure out which is which.

Did the vaccine reduce symptomatic infections? No vaccine is 100% protective. The best of the bunch, like vaccines against the measles and hepatitis A, reduce infections in about 95% of people. Yet many other vaccines, such as those for influenza and typhoid, are closer to a

What is the target for Covid-19 vaccines? The FDA has set an efficacy threshold of a 50% reduction in symptomatic infections for consideration of licensure (total and severe infections are harder to measure — more on that later). But experts would like to see something closer to a 60% to 70% reduction, which would bring us closer to approaching herd immunity and potentially allow us to start relaxing physical distancing measures. This is one reason why the 90% reduction reported this week by Pfizer and BioNTech in the first trial results are particularly exciting.

Who participated in the study? Three groups are key: people older than 65; underrepresented racial and ethnic groups, particularly Black and Latino populations; and individuals with medical conditions such as kidney disease, diabetes, or obesity. Study after study after study has shown that these groups suffer the greatest burden of Covid-19-related complications and death. So a vaccine that reduces disease severity in young, healthy white people but has a little effect in these higher-risk groups might have considerably less public health impact. ...

Is it safe? Since vaccines are mainly given to healthy people — and in this case, potentially to billions of them — understanding the safety of a Covid-19 vaccine is essential. Some good news is that the vaccine candidates under consideration are unlikely to have common severe side effects such as a severe allergic reaction or rash requiring hospitalization. They have completed Phase 2 trials that demonstrated safety in hundreds of people. Any vaccine that caused severe side effects in more than 10% of the Phase 2 participants would not have moved ahead into these larger trials.   ...