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TThe BA.5 version of Covid-19 has become the majority variant of the virus in America in a matter of weeks, in a worrying development that comes amid what may already be the second-biggest wave of the pandemic in America.
It also comes at a time when much of the US has eased nearly all Covid restrictions on the public and life has largely returned to normal.
“Covid-19 is clearly not over yet. We’re seeing dramatic increases in cases and hospitalizations in many places across the United States,” said Jason Salemi, associate professor of epidemiology at the University of South Florida’s College of Public Health.
As BA.5, one of the Omicron subvariants, starts rocking the US, “we’re heading in a bad direction,” Salemi said. “We’ve seen it coming for a while … We’ve seen it go pretty much unabated.”
According to the U.S. Centers for Disease Control and Prevention (CDC), more than one in three Americans lives in a moderate-risk country for Covid, and one in five is at high risk. That’s the highest percentage in the country at risk since February, Salemi said.
More than 100,000 new cases of Covid are now being confirmed in the US every day – a rate that has been fairly constant over the past six weeks. While cases have slowed in the Northeast, surges are now hitting other parts of the country.
At the same time, hospitalizations have been rising steadily since the pandemic’s lowest dip in April – although the rise has not been as sharp and the peak not as high as in previous waves.
“The older you are, the more likely you are to be hospitalized,” Salemi said. “But hospital admissions are increasing for every age group.”
Hospitalizations typically lag behind cases by a few days. But a seemingly stable rate of cases with rising hospital admissions means something else appears to be at play, experts said – likely waning immunity in the face of a more contagious, immune-preventable and pathogenic variant.
The virus is evolving to circumvent the protection against infection offered by vaccination or recovery from a previous illness with Covid, and it also appears to be more easily transmissible.
The immune-avoiding properties of the emerging variants make new waves more likely, says Tulio de Oliveira, director of the Center for Epidemic Response and Innovation at the University of Stellenbosch and leader of the Network for Genomic Surveillance in South Africa.
“BA.4 and 5 are possibly the variants that can most easily breach immunity,” he said. They are “really reinfectible”.
In South Africa, BA.1 — the first Omicron variant — offered very little protection from infection with BA.4 and BA.5, De Oliveira said. According to laboratory studies, the antibodies produced by infection with BA.1 do not protect against reinfection after two or three months.
Infection with BA.2 seemed to offer some protection, possibly because that wave was younger, he said.
But while immunity to infection appears to be low, previous immunity still holds up well against serious outcomes like hospitalization and death.
People who have been vaccinated and those who were previously infected “get sick easily with BA.4 and BA.5, but they will develop very few diseases,” De Oliveira said.
In a preprint study in hamsters, the new variants appear to be much more virulent and pathogenic than previous Omicron variants. But South Africa saw no more severity from BA.4 and 5 than during its other Omicron waves.
That’s because the severity of these variants depends on immunity levels in addition to their intrinsic properties. “Now [severity] is not only a property of the variant itself, but also of the variant and the population it encounters,” said De Oliveira.
Even before this surge, an estimated 95% of South Africans were protected from vaccination or previous bouts of Covid.
“We believe this hybrid immunity in South Africa has sustained our BA.4 and BA.5 wave with very low hospitalizations and deaths,” De Oliveira said.
Even when variants are more pathogenic in the lab, high levels of immunity can help keep serious diseases at bay. It is therefore important to keep up to date on vaccinations.
“The first and second boosters are very important,” Salemi said.
Still, only 34% of eligible Americans — those over the age of five — have received booster doses as recommended by the CDC. While first booster uptake was better in older Americans, the age group at highest risk, second booster uptake was extremely low.
“There’s a lot of opportunity for declining immunity and declining protection from the vaccine without these booster doses to allow these new circulating variants with some perhaps more worrying properties to do a little more damage,” Salemi said. Declining immunity coupled with a more immune-preventable variant means that “you can see an increase in some of these indicators of serious illness.”
The number of 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.
“That will be crucial in the US,” he said. “It’s very different when a new wave comes and hospitals are already overwhelmed.” That’s one of the reasons the delta wave was so deadly, because it was long-lasting and kept hospitals full, he said.
Bags in the US with poor immunity – including those who haven’t been vaccinated recently or have recovered from the virus – could suffer more serious illnesses. But places with high vaccination rates and recent increases are likely to do better when it comes to hospitalizations and deaths, he said.
In South Africa, the wave came quickly and ended quickly – but had a significant economic impact, as people were unable to work due to illness.
To minimize the impact of a surge, including the risk of economic disruption and long-term problems like Long Covid, Americans “need to get the numbers down as soon as possible,” Salemi said.
This includes the same measures that have proven helpful in fighting 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 drastically reduce risk — not just for ourselves and our families, but for many of the members of our community who are very vulnerable.”
As each infection presents new opportunities for the virus to evolve and escape immunity, scientists and officials around the world must continue to monitor it, de Oliveira said.
“This virus has surprised us far too often.”
