Research on seasonal coronaviruses suggests that SARS-CoV-2, the virus that causes the disease, could similarly evolve to evade our immune systems and vaccination efforts, though probably at a slower pace, Scientific American reports.
Influenza may provide the best blueprint of what to expect going forward. The most common flu vaccine—the inactivated virus—is not “truly sterilizing because it doesn’t generate local immune response in the respiratory tract,” says Natasha Crowcroft, senior technical adviser for measles and rubella at the World Health Organization. This fact, coupled with low immunization rates (often shy of 50 percent among adults) and the influenza virus’s ability to infect and move between multiple species, enables it to constantly change in ways that make it hard for our immune system to recognize. Still, depending on the year, flu vaccines have been shown to reduce hospitalizations among older adults by an estimated 40 percent and intensive care admissions of all adults by as much as 82 percent.
Data remain mixed on the relationship between symptoms, viral load and infectiousness. But ample precedent points to vaccines driving successful containment of infectious diseases even when they do not provide perfectly sterilizing immunity. “Measles, diphtheria, pertussis, polio, hepatitis B—these are all epidemic-prone diseases,” Crowcroft says. “They show that we don’t need 100 percent effectiveness at reducing transmission, or 100 percent coverage or 100 percent effectiveness against disease to triumph over infectious diseases.”
Covid-19 vaccine rollouts are finally upon us. They hope that herd immunity—protection from an infectious disease that occurs once a sufficient proportion of the population has been vaccinated or infected—is on the horizon. But even though the first vaccines to receive emergency use authorization from the U.S. Food and Drug Administration are exceptionally effective at preventing COVID-19, data cannot yet tell us if they hinder transmission of SARS-CoV-2, the virus that causes the disease.
