Concerns about SARS-CoV-2 evolution should not hold back efforts to expand vaccination

When vaccines are in limited supply, expanding the number of people who receive some vaccine, such as by halving doses or increasing the interval between doses, can reduce disease and mortality compared with concentrating available vaccine doses in a subset of the population. A corollary of such dose-sparing strategies is that the vaccinated individuals may have less protective immunity. Concerns have been raised that expanding the fraction of the population with partial immunity to SARS-CoV-2 could increase selection for vaccine-escape variants, ultimately undermining vaccine effectiveness. We argue that, although this is possible, preliminary evidence instead suggests such strategies should slow the rate of viral escape from vaccine or naturally induced immunity. As long as vaccination provides some protection against escape variants, the corresponding reduction in prevalence and incidence should reduce the rate at which new variants are generated and the speed of adaptation. Because there is little evidence of efficient immune selection of SARS-CoV-2 during typical infections, these population-level effects are likely to dominate vaccine-induced evolution. In this Perspective, Cobey, Larremore, Grad and Lipsitch argue that dose-sparing regimens of COVID-19 vaccines can reduce disease incidence, prevalence and burden and explain why they think that such strategies would also slow the rate of viral escape from vaccine or naturally induced immunity.

Automated summary

When vaccines are in limited supply, expanding the number of people who receive the vaccine by dose-sparing strategies may reduce disease and mortality, although it could potentially increase the risk of vaccine-escape variants. Preliminary evidence suggests that such strategies could slow the rate of viral escape, as long as vaccination provides some protection against escape variants.