Hopefully you’ve heard the exciting news by now: Last week, both Moderna and Pfizer and BioNTech announced that their COVID-19 vaccines are about 95% effective! This is groundbreaking news that had changed the way that many physicians and public health professionals – including myself – think about these vaccines. But, you may be wondering what does “95% effective” really mean, both for the vaccines themselves and the pandemic? Read on for an explanation.
First, and I cannot emphasize this enough: a 95% effective vaccine is incredible news. The U.S. Food and Drug Administration (FDA) had set a target for COVID-19 vaccines to be at least 50% effective, and many public health experts had been preparing for a vaccine to be between 50-60% effective. This has completely changed the way that we are thinking about this vaccine. In fact, I feel confident in saying that many statements made about COVID-19 vaccines even as recently as 2 or 3 weeks ago are probably outdated now.
To put a 95% vaccine efficacy in context, most years the flu vaccine is between 40 to 60% effective. The pertussis part of the DTaP vaccine is between 80-90% effective in preventing whooping cough. Two doses of the mumps part of the MMR vaccine are about 88% effective against the mumps. On the other hand, two doses of the measles part of MMR vaccine are about 97% effective against the measles. Public health specialists were preparing for COVID-19 vaccine to be similar to a good flu vaccine; instead it looks like it will be more effective than the mumps part of the MMR and almost as effective as the measles part. That’s really good!
A 95% effective COVID-19 vaccine would reduce your risk of infection by 95%. That does not mean that 5% of vaccinated people will get COVID-19 – the percent of vaccinated people who get COVID-19, even during the pandemic, will be much lower. The Pfizer study included over 41,000 volunteers who had received at least 2 doses of either the vaccine or placebo. If we assume that half received vaccine and half received placebo, then that would mean that around 20,500 people received the Pfizer COVID-19 vaccine. In the vaccine group, 8 people, or 0.04%, got COVID-19, compared with 162 people (0.80%) in the placebo (no vaccine) group. As you can see, very few people in either group got COVID-19, but much fewer people in the vaccine group got it than in the placebo group.
It is true that some people who received the vaccine got COVID-19, but this doesn’t mean the vaccine didn’t work. The vaccine is not 100% effective – but neither is any other preventive option. However, it markedly reduces the risk of getting COVID-19. This point might sound like a no-brainer to you, but I consistently hear people ask why bother doing Preventive Action X if they can’t be 100% certain it will work. If you’re wondering the same thing, then I ask you to reframe the question: would you rather have a 1 in 125 chance of getting COVID-19 (0.80%; the risk among unvaccinated people in Pfizer’s study) or a 1 in 2,500 chance (0.04%; the risk among people who got Pfizer’s vaccine)? I’ll take the 1 in 2,500 chance myself.
Of course, physicians don’t only consider the effectiveness of a vaccine or treatment – we also consider the safety. The good news is that both Pfizer and BioNTech and Moderna reported that their vaccines had no serious safety concerns. However, they do appear to cause a lot of soreness at the injection site. In most cases, the soreness gets better on its own in a day or two, but it’s important to expect that.
For now, we only have the companies’ words on their vaccines’ safety and effectiveness, but very soon we’ll be able to learn more about it from vaccine experts. The FDA has announced that they will hold a public meeting of its Vaccines and Related Biological Products Advisory Committee on December 10, 2020. The meeting will be livestreamed on the FDA’s YouTube, Facebook and Twitter accounts. The FDA also plans to make background materials available to the public no later than December 8, 2020. I, for one, plan to read the materials soon after they’re posted and watch the meeting live. Stay tuned for updates!
Stay healthy, have a happy Halloween, and keep wearing your masks!
💉 Dr. B