COVID-19 herd immunity v. learning to live with the virus

• Published in: South African medical journal Vol. 111; no. 9; pp. 852 - 856
• Main Author: Madhi, S A
• Format: Journal Article
• Language: English
• Published: South Africa Health and Medical Publishing Group (HMPG) 01.09.2021; Health & Medical Publishing Group
• Subjects: Control; COVID-19 - epidemiology; COVID-19 - immunology; COVID-19 - virology; COVID-19 Vaccines - administration & dosage; Epidemics; Evaluation; Herd immunity; Humans; Immunity, Herd - immunology; Mutation; Patient Acuity; Public health administration; SARS-CoV-2 - genetics; SARS-CoV-2 - isolation & purification; South Africa; Time Factors; South Africa
• ISSN: 0256-9574; 2078-5135
• DOI: 10.7196/SAMJ.2021.v111i9.16005

Mutations of SARS-CoV-2 have been associated with increased transmissibility and occasionally reduced sensitivity to neutralising antibody activity induced by past ancestry virus infection or current COVID-19 vaccines. Nevertheless, COVID-19 vaccines have consistently demonstrated high efficacy and effectiveness against COVID-19 severe disease, hospitalisation and death, including disease caused by designated variants of concern. In contrast, COVID-19 vaccines are more heterogeneous in reducing the risk of infection and mild COVID-19, and are modestly effective in interrupting virus transmission. Ongoing mutations of SARS-CoV-2 resulting in increased transmissibility and relative evasion of neutralising antibody activity induced by past virus infection or COVID-19 vaccines are likely. The duration of protection induced by COVID-19 vaccines is modelled to be relatively short in protecting against infection and mild COVID-19, but is likely to be 2 - 3 years against severe disease. Current experience from the UK and Israel demonstrates that even with high levels of COVID-19 vaccine coverage (>85% of the adult population), resurgences with new variants of concern remain a strong probability. Nevertheless, such resurgences are not mirrored by high rates of hospitalisation and death compared with what was experienced in relatively COVID-19 vaccine-naive populations. Even though COVID-19 vaccines are unlikely to result in a herd immunity state, their ability to protect against severe COVID-19 and death could allow for a return to normalcy once a large enough proportion of the adult population in a country has been vaccinated.