Considerations in boosting COVID-19 vaccine immune responses

• Published in: The Lancet (British edition) Vol. 398; no. 10308; pp. 1377 - 1380
• Main Authors: Krause, Philip R, Fleming, Thomas R, Peto, Richard, Longini, Ira M, Figueroa, J Peter, Sterne, Jonathan A C, Cravioto, Alejandro, Rees, Helen, Higgins, Julian P T, Boutron, Isabelle, Pan, Hongchao, Gruber, Marion F, Arora, Narendra, Kazi, Fatema, Gaspar, Rogerio, Swaminathan, Soumya, Ryan, Michael J, Henao-Restrepo, Ana-Maria
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 09.10.2021; Elsevier Limited; Elsevier; Published by Elsevier Ltd
• Subjects: Antigens; Asymptomatic; Coronaviruses; COVID-19; COVID-19 - epidemiology; COVID-19 - immunology; COVID-19 - prevention & control; COVID-19 - virology; COVID-19 vaccines; COVID-19 Vaccines - administration & dosage; COVID-19 Vaccines - adverse effects; COVID-19 Vaccines - immunology; Disease transmission; Evidence-Based Medicine - methods; Evidence-Based Medicine - standards; Evidence-Based Medicine - statistics & numerical data; Guillain-Barre syndrome; Humans; Immune response; Immunity; Immunization, Secondary - methods; Immunization, Secondary - standards; Immunization, Secondary - statistics & numerical data; Immunogenicity, Vaccine; Infections; Life Sciences; mRNA vaccines; Observational Studies as Topic; Pandemics; Pandemics - prevention & control; Public health; Randomized Controlled Trials as Topic; SARS-CoV-2 - immunology; SARS-CoV-2 - pathogenicity; Severe acute respiratory syndrome coronavirus 2; Treatment Outcome; Vaccines; Viewpoint; Viral diseases; United States > US; Israel
• ISSN: 0140-6736; 1474-547X; 1474-547X
• DOI: 10.1016/S0140-6736(21)02046-8

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. If unnecessary boosting causes significant adverse reactions, there could be implications for vaccine acceptance that go beyond COVID-19 vaccines. [...]widespread boosting should be undertaken only if there is clear evidence that it is appropriate. Among vaccinated people, more of the severe disease could be in immunocompromised individuals, who are plausibly more likely to be offered and seek vaccination even though its efficacy is lower than it is in other people.2 Test-negative designs, which compare vaccination status of people who tested positive and those who tested negative, can sometimes reduce confounding,8 but do not prevent distortion of results due to the so-called collider bias.9 The probability that individuals with asymptomatic or mild COVID-19 infection will seek testing might be influenced by whether they are vaccinated. Mean follow-up was, however, only about 7 person-days (less than expected based on the apparent study design); perhaps more importantly, a very short-term protective effect would not necessarily imply worthwhile long-term benefit.12 In the USA, large numbers of adults are fully vaccinated, large numbers are unvaccinated, and systematic comparisons between them are ongoing.