After more than a year of obsessively tracking the number of Covid-19 cases, epidemiologists are beginning to shift focus to other measures as the next stage of the pandemic emerges.
With rich countries vaccinating increasing proportions of their vulnerable populations, the link between the number of infections and deaths appears to be decreasing. Now the focus is on learning to live with the virus and the data that matters most to avoid further crashes.
“We may get to the stage of just monitoring hospitalizations,” said Jennifer Nuzzo, an epidemiologist at the Johns Hopkins University Coronavirus Resource Center, who has built one of the most comprehensive platforms for tracking the virus and its impact.
Before vaccination campaigns took off in the United Kingdom, the United States and Europe, an increase in cases almost invariably translated into an increase in hospitalizations and deaths over the course of several weeks. The strain on healthcare systems left leaders with no choice but to put the brakes on public life, disrupt economies and force people with other medical conditions to delay important procedures.
Now, scientists and government officials are eager to see if the increasing reach of vaccines will finally break that cycle. Events in Britain are providing the most compelling test case to date.
About 46% of the UK population is fully vaccinated, according to Bloomberg’s Vaccine Tracker, helping reduce daily deaths to the lowest level since last summer. However, cases of the delta variant, a more transmissible strain first identified in India, nearly doubled last week, Public Health England said on Friday. Hospitalizations also increased, although most patients have not been fully vaccinated.
Prime Minister Boris Johnson on Monday postponed the end of the lockdown measures by four weeks to allow more adults to receive a second dose of the vaccine, which data shows significantly increases protection against the new strain. But even if the virus spreads further among unvaccinated children and young adults, the real test of the immunization campaign will be whether hospitalizations and deaths remain low.
If they do, Covid would start to look less like an unmanageable pandemic and more like a seasonal illness like influenza. For policy makers, that is the goal.
“Our goal is to live with this virus as we do with the flu,” Health Secretary Matt Hancock told Parliament last week.
Scientists say comparing the prevalence of Covid to the flu, which kills about 650,000 people worldwide each year, will become an important yardstick next fall and winter. Covid has killed more than 3.8 million people since the beginning of 2020, but vaccinated countries should be able to treat their periodic resurgences the same way they do with the flu, and make political decisions accordingly.
“Comparing to the impact of seasonal flu is appropriate when it comes to things like school closings,” Nuzzo said. “What do we do with the flu? Would we do this in a normal flu season? “
Vaccines and variants
In a sign of pandemic optimism, or fatigue, about two dozen US states have reduced the frequency with which they release Covid data. Florida now reports only once a week.
In much of the world, however, health officials are still not taking their eyes off the case numbers. China and Taiwan cut new infections to near zero, but the lack of vaccines means that even small outbreaks must be treated as big threats.
In Taiwan, after a year of relative calm and single-digit daily cases, daily infections rose to 723 during May. The government closed entertainment venues and restricted indoor gatherings to five people to curb the spread.
“When we look at Taiwan, which is the best of the best, it underscores the vulnerability of these countries,” Nuzzo said. “They won’t be able to relax until they can vaccinate more widely.”
With a population of 24 million, Taiwan has administered just over a million doses of vaccines. Mainland China, which has experienced severe lockdowns, is grappling with high levels of vaccine hesitancy and has administered nearly a billion doses, enough to fully vaccinate about a third of its population.
Risk of hospitalization
Even among vaccinated populations, the number of cases remains significant. The more the virus circulates, the more likely it is to mutate into strains that are more lethal or resistant to existing vaccines.
People infected with the delta variant are more than twice as likely to end up hospitalized as those with the alpha strain, according to research by scientists from Scotland published in The Lancet. Although the variant is effectively controlled by vaccines, the threat to health care systems of even a small jump in cases could continue to increase if the virus mutates into more potent forms.
Reaching zero cases is not realistic in the short term, even in highly vaccinated countries. Most societies have come to accept the reality of mutation with other viruses, such as influenza, and incorporate the new strains into vaccines when they emerge. That is likely to be the case for Covid.
“We have to live with the fact that there will be new variants,” said Marc Baguelin, an epidemiologist at Imperial College London. “It’s something that always happens in the background.”