The BA.5 version of Covid-19 has become the predominant variant of the virus in America for several weeks, in an alarming development that comes amid what may already be the second-largest wave of the pandemic in America.
It also comes at a time when much of the US has eased almost all public Covid restrictions and life has largely returned to normal.
“Covid-19 is clearly not over. We are seeing a dramatic increase in the number of cases and hospitalizations in many places in the United States,” said Jason Salemi, associate professor of epidemiology at the University of South Florida College of Public Health.
As the BA.5, one of the Omicron sub-variants, begins to hit the U.S., “we’re moving in a bad direction,” Salemi said. “We’ve seen it coming for a while … We’ve seen it go pretty steadily.”
More than one in three Americans live in a county at medium risk for Covid, and one in five are at high risk, according to the US Centers for Disease Control and Prevention (CDC). This is the highest share of the country facing risks since February, Salemi said.
There are now more than 100,000 new cases of Covid confirmed in the US every day – a rate that has been fairly steady over the past six weeks. While cases in the northeast have declined, waves are now hitting other parts of the country.
There are many opportunities to weaken immunity and weaken vaccine protection without these booster doses to allow these new circulating variants with some perhaps more worrisome characteristics to do a little more damage Jason Salemi
At the same time, hospitalizations have been rising steadily since their pandemic trough in April — although the rise has not been as sharp, nor has the peak been as high as previous waves.
“The older you are, the more likely you are to be hospitalized,” Salemi said. “But hospitalizations are increasing for every age group.”
Hospitalizations usually lag behind cases by several days. But the seemingly stable case rate with rising hospitalizations means something else appears to be at play, experts said — possibly a weakening of immunity in the face of a more infectious, immune-evading, pathogenic variant.
The virus has evolved to avoid the protection from infection offered by vaccination or recovery from a previous illness with Covid, and also appears to be more transmissible.
The immune-resistant properties of evolving variants make new waves more likely, says Tulio de Oliveira, director of the Center for Epidemic Response and Innovation at Stellenbosch University and head of the South African Genome Surveillance Network.
“BA.4 and 5 are potentially the variants that can break through immunity most easily,” he said. They are “really capable of re-infection”.
In South Africa, BA.1 — the first omicron variant — offers very little protection against infection with BA.4 and BA.5, de Oliveira said. Antibodies generated by BA.1 infection do not protect against reinfection after two or three months, according to laboratory studies.
There are simple steps we can take to dramatically reduce the risks – not only to ourselves and our families, but also to many of those members of our community who are very vulnerable. Jason Salemi
BA.2 infection appeared to offer some protection, possibly because this wave was more recent, he said.
But while immunity to infection appears to be low, preexisting immunity still holds up well against severe outcomes such as hospitalization and death.
People who have been vaccinated and those who have been infected before “will easily acquire BA.4 and BA.5, but will develop very little disease,” de Oliveira said.
In a preprint study on hamsters, the new variants appear to be much more virulent and pathogenic than previous omicron variants. But South Africa did not see more burden from BA.4 and 5 than during the other omicron waves.
This is because the severity of these variants depends on immunity levels in addition to their intrinsic properties. “Now [severity] is a property not only of the variant itself, but also of the variant and the population it encounters,” de Oliveira said.
Even before this surge, around 95% of South Africans were thought to have protection from vaccination or previous bouts of Covid.
“We believe that this hybrid immunity in South Africa is what is keeping our BA.4 and BA.5 wave with very low hospitalizations and deaths,” de Oliveira said.
Even if variants are more pathogenic in the laboratory, high levels of immunity can help prevent severe disease. That’s why keeping up-to-date on vaccination information is key.
“The first and second boosters are very important,” Salemi said.
Yet only 34% of eligible Americans—those over the age of 5—received booster doses, as recommended by the CDC. While uptake of the first booster is better among older Americans, the age group at highest risk, uptake of the second booster is extremely low.
“There’s a lot of opportunity to weaken immunity and weaken vaccine protection, without these booster doses, to allow these new circulating variants with some perhaps more worrisome characteristics to do a little more damage,” Salemi said. A weakened immune system combined with a more immune-evasive variant means “you may start to see an increase in some of these indicators of severe disease.”
Deaths in South Africa also remained low largely because hospitals were not overwhelmed. “When the BA.4 and BA.5 waves started, we had completely empty intensive care units – so anyone who got sick could get good support,” de Oliveira said.
“This will be key in the US,” he said. “It’s very different if another wave comes and the hospitals are already full.” That’s one reason the Delta wave was so deadly because it lingered for a long time and kept the hospitals full, he said.
Parts of the U.S. with weak levels of immunity — including those who haven’t recently been vaccinated or have had the virus — may experience more severe disease. But places with high vaccination rates and recent spikes are likely to do better when it comes to hospitalizations and deaths, he said.
In South Africa, the wave came quickly and ended quickly too – but there were significant economic effects, with people unable to work due to illness.
To minimize the effects of the surge, including the risk of economic shocks and long-term problems like prolonged Covid, Americans need to “get the numbers down as quickly as possible,” Salemi said.
This includes taking the same measures that have proven to help deal with the virus in the past: vaccines, masks, distancing, ventilation, testing.
“Please don’t think of mitigation as all or nothing,” Salemi said. “There are simple steps we can take to dramatically reduce the risks – not only to ourselves and our families, but to many of those members of our community who are very vulnerable.”
Because each infection offers new opportunities for the virus to evolve and evade immunity, scientists and officials around the world must continue to monitor it, de Oliveira said.
“This virus has surprised us too many times.”
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