Not long ago, I wrote a post about the COVID-19 vaccine produced by Pfizer. At that time, I only had access to the results of the small clinical trial, but those results were very encouraging. Now, the initial results of the large clinical trial are available, and they are even more encouraging. In short, the vaccine is 95% effective at preventing symptomatic cases of COVID-19 in the group that was being tested. While there were side effects, they were generally mild. Of course, not all kinds of people were tested. People under 16 years of age were not included in the clinical trial. Neither were pregnant women nor those who are immunocompromised. Thus, the results don’t apply to people in those groups.
Like most clinical trials used for licensure of a medication, this was a large-scale, placebo-controlled, double-blind study. That means a large number of people (43,538) were randomly assigned to receive either two doses of a placebo (an injection of saltwater) or two doses of the vaccine. The doses were separated by 21 days. Neither the people getting the injections nor the researchers directly involved in the study were aware of which injection each person got (that’s what “double blind” means). Once there were enough COVID-19 cases among all the participants to make a reasonable conclusion about the results, the researchers learned which injection each participant got. At that point, they could compare the two groups.
When they made the comparison, they found that starting seven days after the second dose, there were only 8 cases of COVID-19 in the group that got the vaccine doses, while there were 162 among those who got the saltwater injections. Thus, the vaccine clearly provides strong protection against COVID-19, at least among people like those who were in the study. Now please understand that people in the study were only tested for COVID-19 if they exhibited symptoms, so this says nothing about whether or not the vaccine protects against asymptomatic COVID-19 infections.
Of course, the small clinical trials had already shown that the vaccine would be effective at preventing symptomatic cases of COVID-19. This large-scale trial was done to confirm that result and, more importantly, to determine whether or not the vaccine is safe for the majority of people. While it is impossible to know for sure, all indications are that for people over 16 who are not pregnant and not immunocompromised, the vaccine is safe. The vast majority of vaccine recipients reported pain at the injection site, compared to only a small percentage of those who got the placebo. Small percentages of those who got the vaccine also reported redness and swelling at the injection site.
The most commonly-reported side effect after pain at the injection site was fatigue. In people aged 16-55, for example, 59% of those receiving the vaccine reported fatigue after the second dose, compared with 23% of those who got the placebo. The percentages were slightly lower for those over 55. Headache was the next most common side effect, followed by muscle pain, chills, joint pain, fever, diarrhea, and vomiting. Figure 2 from the study gives a good summary. There were a total of four people who had severe reactions to the vaccine. Those reactions were a shoulder injury related to administration of the vaccine, severely swollen lymph nodes, an abnormal heart rhythm, and unexplained severe sensations in the leg. There were two vaccine recipients who died, but there were four placebo recipients who died. None of the deaths were judged to be related to the clinical trial.
Based on these results, I plan to get the vaccine as soon as I am allowed to. My wife is in a high-risk group, and she will as well. My adult daughter and her husband have a business that requires extensive travel throughout the U.S. They will also be getting it. Whether or not you or your family get this vaccine (or one of the others that will no doubt become available over time) is up to you. Medical decisions are deeply personal and should be made in consultation with a physician who knows your medical history. I would never presume to tell anyone how to make such decisions. I simply wanted to communicate to my readers what I think the data say about this vaccine.
I will add one more thing. One of my readers said that she heard the COVID-19 vaccine can make women unable to have babies, because the vaccine is training the body’s immune system to fight a protein that is similar to syncytin-1, a protein important to the formation of a placenta. Thus, it is possible that a woman who gets pregnant after getting the vaccine will be unable to form a placenta. While it is true that the proteins are similar, their similarity is in their function, not their actual structure. Both proteins facilitate connection to a membrane, but they do so in very different ways. As a result, their structures are quite different, and a protein’s structure is what the immune system attacks. Thus, there is no reason to expect that the vaccine will cause the immune system to attack syncytin-1.
In addition, women who contract the actual disease would have the same problem, since the immune system attacks the same protein whether it comes from the instructions given by the vaccine or the virus itself. I don’t know of any reports indicating that women who contracted COVID-19 are unable to form a placenta. Finally, while pregnant women were excluded from the trial, 23 got pregnant during the trial. Twelve of them were in the group that got the vaccine. They are being followed, and as of the December 4th National Vaccine Advisory Committee meeting, no adverse effects have been found.