TO THE EDITOR
Citing preliminary immunogenicity results and one study on effectiveness, Offit (Feb. 9 issue)1 argues in his Perspective article that the bivalent boosters against SARS-CoV-2 omicron subvariants BA.4 and BA.5 as well as the ancestral strain should not be deployed throughout the entire population. Key available evidence that was omitted by Offit suggests otherwise.
Davis-Gardner and colleagues, as well as others, found that the bivalent boosters had better immunogenicity against emerging variants, including BQ.1.1 and XBB, than did the monovalent boosters.2 Coronavirus disease 2019 (Covid-19) has taken a tremendous toll on the entire population and resulted in more than 7500 hospitalizations and 1100 deaths in the United States among persons 18 to 49 years of age between September and December 2022 alone, according to the Centers for Disease Control and Prevention. Several studies indicate that the bivalent boosters are clinically effective in reducing the incidences of symptomatic disease, hospitalization, and death across the age spectrum, including among persons 18 to 49 years of age who had been vaccinated previously.3-5 Given the excellent safety profile of the vaccines, which is similar to that of the influenza vaccine among persons 6 months of age or older, the totality of the available evidence supports the vaccination of all currently eligible persons with updated Covid-19 vaccines as an important public health intervention.
Peter W. Marks, M.D., Ph.D.
Robert M. Califf, M.D.
Food and Drug Administration, Silver Spring, MD
peter.marks@fda.hhs.gov
No potential conflict of interest relevant to this letter was reported.
This letter was published on March 1, 2023, at NEJM.org.
RESPONSE
The author replies: Marks and Califf reference a study by Davis-Gardner and colleagues1 that showed that a bivalent vaccine containing the ancestral strain of SARS-CoV-2 plus the BA.4 and BA.5 subvariants had improved immunogenicity as compared with the monovalent ancestral booster against BQ.1.1 and XBB.1. Specifically, this bivalent vaccine resulted in levels of neutralizing antibodies against BA.1.1 and XBB.1 that were 1.5 times and 2.6 times, respectively, those that were observed with the use of the monovalent booster. Neither of these increases, however, is likely to be clinically significant.
Representatives of Moderna found that a bivalent booster vaccine containing BA.1 that induced a level of neutralizing antibodies that was higher than that with the monovalent vaccine by a factor of 1.75 did not result in significantly better protection against Covid-19 in two prospective, randomized, controlled studies.2,3 Marks and Califf correctly note that bivalent boosters have enhanced protection against symptomatic disease in 18-to-49-year-olds, at least in the short term. However, the protection against hospitalization that was afforded by bivalent boosters, which is the goal of this vaccine, was limited to people over 65 years of age4 and those with a median age of 76.5 Booster administration should be targeted to the groups most likely to be hospitalized — specifically, persons who are elderly or immunocompromised, have multiple coexisting conditions, or are pregnant.
Paul A. Offit, M.D.
Children’s Hospital of Philadelphia, Philadelphia, PA
Since publication of his article, the author reports no further potential conflict of interest.
This letter was published on March 1, 2023, at NEJM.org.
https://www.nejm.org/doi/full/10.1056/NEJMc2301323
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