Weekend Long Reads: COVID-19 and the Flu

by Kevin Schofield

This weekend's "long read" is a column from Dr. Arnold S. Monto, an epidemiologist at the University of Michigan School of Public Health. Our hopes that COVID-19 could be eradicated, he says, were based on faulty assumptions, and we now need to shift to planning for how we will deal with the virus for the foreseeable future — much the same way that we manage influenza.

The notion that we can eliminate COVID-19 has been rooted in the concept of "herd immunity": Once enough people gain immunity through exposure or vaccination, further transmission paths become increasingly scarce and the virus simply dies out. But herd immunity depends on two factors: low transmission and eliminating pockets of susceptible people. The delta variant has blown both of those away; it's highly transmissible, and some number of vaccinated individuals have still contracted it (though, for the most part, they either remain asymptomatic or develop only mild cases).

If COVID-19 isn't going away, that means we need to adjust to living with it — and influenza is one model for how we might do that. Vaccinations will still be important, but, as with flu shots, the model will focus on re-vaccinations at regular intervals instead of "one and done." Doctors recommend an annual flu shot for two reasons: first, because our immunity wanes over time; and second, because of "antigenic drift," ongoing mutations in the virus such as we have seen with the delta variant. Twice a year, the World Health Organization updates its recommendations for which influenza strains should be targeted by flu shots, and we can expect that a similar process will emerge for COVID-19 vaccination development.

At the moment, the best COVID-19 vaccines are over 90% effective in preventing symptomatic infection; that is far better than the 50—60% effectiveness on average for flu shots, and will help keep COVID-19 at bay for as long as we can sustain it. We still don't have good data on how fast vaccine-based immunity wanes, though, and we are only just beginning to understand the patterns of antigenic drift in COVID-19, so it's too early to predict how often we will need COVID-19 shots.

There is one other piece of good news, though: Effective therapeutics and antiviral medicines are coming onto the market now. If vaccines can continue to substantially reduce the number of severe COVID-19 cases, and medicines exist to treat the cases that do occur, we may quickly learn to live with this.

The Future of SARS-CoV-2 Vaccination — Lessons from Influenza

Featured image is attributed to quapan (under a Creative Commons, CC BY 2.0 license).