With rapid vaccination campaign, strict lockdown may prevent emergence of resistant viruses

New model highlights possible policy strategy

The COVID-19 pandemic led to an unprecedented global response in the form of social distancing and lockdown. Currently, the greatest hope rests on global vaccination against the virus. This is based on the assumption that social and economic activities can gradually be revived as more and more people are vaccinated. However, a relaxation of social distancing combined with increased selection pressure on the virus from vaccination is likely to lead to the development of vaccine resistance. Scientists at Harvard University, together with scientists from Israel and the Max Planck Institute for Evolutionary Biology in Plön, Germany, have studied a model for how to avoid this effect.

The researchers analyzed the evolutionary dynamics of the corona virus as a function of the factors intensity of social distancing and speed of the vaccination campaign. To do this, they evaluated data from Israel, the United States, Brazil, France, and Germany to calculate the likelihood of the emergence of a vaccine-resistant virus under certain conditions.

So what policies would minimize the likelihood of resistant viruses?

If vaccination rates are slow, the emergence of vaccine-resistant mutants is inevitable, according to the researchers' calculations. In this way, the virus gets ample time and opportunity to evolve, and mutations can become so well established. In rapid vaccination campaigns (such as those conducted in Israel), the emergence of resistance can be avoided under certain circumstances, namely if a strict lockdown is maintained during the process. This reduces the number of infected individuals and thus the size of the virus population. The population thus reduced produces fewer mutations, so the likelihood of new variants becoming established in the vaccinated population can be significantly reduced.
With these results, the researchers hope to provide guidelines for a combined policy of vaccination campaigns and social distancing that would minimize the likelihood of resistant mutants emerging, for current and also future vaccination campaigns.