These excerpts are posted by Eric Zuesse
Viewpointwww.thelancet.com Published online September 13, 2021
Office of Vaccines Research and Review, Food and Drug Administration, Silver Spring, MD, USA (P R Krause MD, M F Gruber PhD); Department of Biostatistics, University of Washington, Seattle, WA, USA (Prof T R Fleming PhD); Nuffield Department of Population Health, University of Oxford, Oxford, UK (Prof R Peto FRS); Department of Biostatistics, University of Florida, Gainesville, FL, USA (Prof I M Longini PhD); University of the West Indies, Mona, Jamaica (Prof J P Figueroa PhD); Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK (Prof J A C Sterne PhD, Prof J P T Higgins PhD); Universidad Nacional Autónoma de México, DF, Mexico (A Cravioto PhD); Wits Reproductive Health and HIV Institute, Johannesburg, South Africa (Prof H Rees MD); Centre of Research in Epidemiology and Statistics (CRESS), Université de Paris, Paris, France (Prof I Boutron PhD); MRC Population Health Research Unit, University of Oxford, Oxford, UK (Prof H Pan PhD); The INCLEN Trust International, New Delhi, India (Prof N Arora MD); World Health Organization, Geneva, Switzerland (F Kazi PhD, R Gaspar PhD, S Swaminathan MD, M J Ryan MD, A-M Henao-Restrepo MD) Correspondence to: Dr Philip R Krause Office of Vaccines Research and Review, Food and Drug Administration, Silver Spring, MD 20993, USA email@example.com or Dr Ana-Maria Henao-Restrepo World Health Organization, Geneva 1211, Switzerland firstname.lastname@example.org
THE ARTICLE’S OPENING:
A new wave of COVID-19 cases caused by the highly transmissible delta variant is exacerbating the worldwide public health crisis, and has led to consideration of the potential need for, and optimal timing of, booster doses for vaccinated populations.1 Although the idea of further reducing the number of COVID-19 cases by enhancing immunity in vaccinated people is appealing, any decision to do so should be evidence-based and consider the beneﬁts and risks for individuals and society. COVID-19 vaccines continue to be eﬀective against severe disease, including that caused by the delta variant. Most of the observational studies on which this conclusion is based are, however, preliminary and diﬃcult to interpret precisely due to potential confounding and selective reporting. Careful and public scrutiny of the evolving data will be needed to assure that decisions about boosting are informed by reliable science more than by politics. Even if boosting were eventually shown to decrease the medium-term risk of serious disease, current vaccine supplies could save more lives if used in previously unvaccinated populations than if used as boosters in vaccinated populations.
Boosting could be appropriate for some individuals in whom the primary vaccination, deﬁned here as the original one-dose or two-dose series of each vaccine, might not have induced adequate protection — eg, recipients of vaccines with low eﬃcacy or those who are immunocompromised2 (although people who did not respond robustly to the primary vaccination might also not respond well to a booster). It is not known whether such immunocompromised individuals would receive more beneﬁt from an additional dose of the same vaccine or of a diﬀerent vaccine that might complement the primary immune response.
Boosting might ultimately be needed in the general population because of waning immunity to the primary vaccination or because variants expressing new antigens have evolved to the point at which immune responses to the original vaccine antigens no longer protect adequately against currently circulating viruses.
Although the beneﬁts of primary COVID-19 vaccination clearly outweigh the risks, there could be risks if boosters are widely introduced too soon, or too frequently, especially with vaccines that can have immune-mediated side-eﬀects (such as myocarditis, which is more common after the second dose of some mRNA vaccines,3 or Guillain-Barre syndrome, which has been associated with adenovirus-vectored COVID-19 vaccines4). If unnecessary boosting causes signiﬁcant adverse reactions, there could be implications for vaccine acceptance that go beyondCOVID-19 vaccines. Thus, widespread boosting should be undertaken only if there is clear evidence that it is appropriate. Findings from randomised trials have reliably shown the high initial eﬃcacy of several vaccines, and, less reliably, observational studies have attempted to assess the eﬀects on particular variants or the durability of vaccine eﬃcacy, or both. The appendix identiﬁes and describes the formal and informal reports from these studies. Some of this literature involves peer-reviewed publications; however, some does not, and it is likely that some details are importantly wrong and that there has been unduly selective emphasis on particular results.Together, however, these reports provide a partial but useful snapshot of the changing situation, and some clear ﬁndings emerge. The ﬁgure summarises the reports that estimated vaccine eﬃcacy separately for severe disease (variously deﬁned) and for any conﬁrmedSARS-CoV-2 infection, plotting one against the other. A consistent ﬁnding is that vaccine eﬃcacy is substantially greater against severe disease than against any [covid-19] infection; in addition, vaccination appears to be substantially protective against severe disease from all the main viral variants. Although the eﬃcacy of most vaccines against symptomatic disease is somewhat less for the delta variant than for the alpha variant, there is still high vaccine eﬃcacy against both symptomatic and severe disease due to the delta variant.
Current evidence does not, therefore, appear to show a need for boosting in the general population, in which eﬃcacy against severe disease remains high. Even if humoral immunity appears to wane, reductions in neutralising antibody titre do not necessarily predict reductions in vaccine eﬃcacy over time, and reductions in vaccine eﬃcacy against mild disease do not necessarily predict reductions in the (typically higher) eﬃcacy against severe disease. This eﬀect could be because protection against severe disease is mediated not only by antibody responses, which might be relatively short lived for some vaccines, but also by memory responses and cell-mediated immunity, which are generally longer lived.5 The ability of vaccines that present the antigens of earlier phases of the pandemic (rather than variant-speciﬁc antigens) to elicit humoral immune responses against currently circulating variants6,7 indicates that these variants have not yet evolved to the point at which they are likely to escape the memory immune responses induced by those vaccines. ...
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