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I should be very easy to design new vaccines to target the new variants (e.g. the first mRNA vaccine prototypes were designed days after the SARS-CoV-2 genetic sequence was made public). Indeed, both Pfizer and Moderna started trials to measure the effectiveness of a booster against the Beta variant (which shows some difficulty with developing boosters to the variants -- the circulating variants can change before clinical trials finish). Recently, Pfizer has begun trials for a booster against the Delta variant.
However, there may be some scientific and social issues related to developing new boosters against the variants:
However, there may be some scientific and social issues related to developing new boosters against the variants:
https://www.nature.com/articles/s41577-021-00592-1To counteract the impact of viral variants, one suggestion is to develop new vaccines that more closely reflect the circulating viruses. For example, Moderna has developed a novel vaccine targeting the B.1.1.7 VOC, which has been tested in preclinical trials57 and is now in clinical trials (NCT04785144). However, it is not clear how beneficial such vaccines designed specifically to target new variants will be. The main consideration will be how far the circulating viruses in autumn 2021 (when booster vaccination has been proposed in some countries) will have drifted antigenically from the original reference sequence of the SARS-CoV-2 S protein used for the first-generation vaccines. Although studies relating to the VOCs have shown reduced neutralization in vitro, there has been no significant reported impact on vaccine effectiveness, which suggests that the viral mutations predominantly increase transmissibility, but not necessarily immune escape. As the current vaccines still offer good protection against severe disease, there may be limited return on a new variant booster. Indeed, there may actually be negative unintended consequences. The first is that producing a new booster vaccine for the countries with sufficient income to afford substantial coverage with the first-generation vaccines may reduce manufacturing capacity for doses for lower-income countries. Second, boosting with a similar antigen may boost the antibody response to the original strain rather than prime for antibodies specific to the new strain58. This idea of ‘original antigenic sin’ refers to the boosting of responses to previously seen epitopes to the detriment of responses to new epitopes, particularly when they are closely related. Such a phenomenon has been observed for influenza, with individuals who were recently immunized with seasonal influenza vaccine producing lower antibody responses to 2009 pandemic influenza than previously unimmunized individuals59. Furthermore, the variants may be drifting apart, and so priming with a variant might narrow rather than broaden protection. It is our opinion that engineering novel booster vaccines should not be a priority at this time.
Whereas engineering new variant vaccines may not be beneficial, an alternative strategy is to boost immunity with a third dose of vaccine targeting the initial reference strain