The Food and Drug Administration and the Centers for Disease Control and Prevention recently approved another booster shot of the Pfizer / BioNTech and Moderna COVID-19 vaccines for those 50 years and older. The recommendation follows a study from Israel recently published in The New England Journal of Medicine.
The Israel study reports a modest relative risk reduction in COVID-19 infections for those receiving a new booster compared to those who received a booster, on the order of 1.5 times lower, with this benefit decreasing during the study period, or about two months.
The study also reported a significant relative risk reduction in severe cases of COVID-19 following another booster, on the order of 3.5 times lower, and this benefit lasted during the study period. It is not yet known whether this benefit will continue in the future.
An additional takeaway from the study is the absolute risk reduction for severe cases.
According to the study data, there were about 3.9 serious cases per. 100,000 personal days for those who had received two vaccine doses and a booster. This measurement, personal days, is difficult to get a practical understanding of – it assumes that the serious case frequency scales in the same way with both the size of the population and over time.
The 3.9 serious cases per 100,000 personal days corresponds to 3.9 serious cases per 1,666 people during the two-month study period, or a rate of severe case for every 420 people who have received two doses and a booster.
Using this same scaling method with two boosters resulted in a rate of one severe case per. 1,111 people.
The benefit of this exercise is that, as a starting point, the benefit of two vaccine doses and one booster is already quite good, considering that all study participants were 60 years and older. The second booster provides an added benefit of risk reduction.
The CDC has reported the benefits of two doses and one booster versus only two doses. In all cases, protection decreases over time, which is what provoked the need for a booster and prompted the need for and discussion of another booster.
Are you going to benefit from an extra booster at this point?
The Israeli study was for those 60 and older, while the recommendation in the United States is for those 50 and older. This younger age limit is similar to when hospitalizations and deaths begin to rise in the U.S. population. So anyone in this group who is risk-averse and wants to gain benefits against severe COVID-19 can choose another booster.
On the other hand, if you are confident in the risk reduction benefit offered by two doses and a booster, including its decreasing protection over time, then you can choose to go past the other booster for now and choose a wait-and-see approach , as more data becomes available.
Like all observational studies, there are limitations to the conclusions that can be drawn from the Israeli study. Moreover, the duration of the study only provides an insight into a narrow time window with risk reduction and benefits. The effect of new variants that may emerge is also unknown.
There are no easy answers and many difficult questions. Experts offer the best advice available in a fog of data uncertainty that is likely to remain stubbornly in place in the short term.
Nevertheless, it is clear that another booster provides some risk reduction. The question is whether that benefit is sufficient enough for a particular person to choose another booster at present.
Sheldon Jacobson is Professor of Computer Science at the University of Illinois at Urbana-Champaign. © 2022 Chicago Tribune. Distributed by Tribune Content Agency.