Some people are concerned that another Covid surge is imminent, fueled by the highly contagious BA.2 subvariant of omicron.
But experts say a significant rise in cases is unlikely, at least for now – possibly due to a recent estimate that almost all Americans currently have some level of Covid antibodies in their systems.
An estimated 95% of Americans aged 16 and over have developed identifiable Covid antibodies, according to a Centers for Disease Control and Prevention survey of blood donor samples conducted in December and updated last month. These come from both vaccinations — about 77% of the US population has received at least one dose of Covid vaccine, according to the CDC — and from previous Covid infections.
That’s one possible reason why some experts, including senior White House medical adviser Dr. Anthony Fauci, do not expect another sharp rise in Covid cases just yet – despite BA.2 rising across Europe and cases of the subvariant have doubled in the last three weeks in the US
That’s certainly good news, but that doesn’t mean it’s never going to rise. Antibodies are transient, with some going away faster than others. Some of them don’t help your body fight the virus at all. And the unpredictability of the virus means few forecasts can ever be fully trusted.
The CDC’s poll confirms this, estimating that as of June 2021 – ahead of the July peak of the Delta variant in the US – more than 87% of Americans had Covid antibodies in their systems. With that in mind, experts would like to share the following with you about the current antibody levels in the country:
Different types of immunity provide protection for different periods of time
The 95 percent estimate is “probably close to accuracy,” says Dr. Timothy Brewer, professor of medicine in the Department of Infectious Diseases at UCLA’s David Geffen School of Medicine. But there is a potentially big difference between people who got their antibodies from Covid vaccines and people who got them solely from previous infections.
Antibodies from vaccinated people tend to decline about four to six months after vaccination, Brewer says. So if you received a booster dose in December, your antibody boost will likely wear off between April and June.
The data surrounding so-called “natural immunity” is much more mixed.
According to an October 2021 Yale School of Public Health study published in The Lancet Microbe, unvaccinated people could be immune to reinfection for three to 61 months after contracting Covid. The study authors wrote that more data is needed to confirm these results, noting that their research did not include variants like Omicron or subvariants like BA.2.
Another study in the journal Science, published in January 2022, found that natural immunity can last up to eight months. And a CDC study published in September 2021 showed that about a third of participants with Covid had not developed an apparent natural immunity.
“I’m not aware of any good data on the duration of antibodies from a natural infection,” says Brewer.
According to a study published in the National Library of Medicine last August, unvaccinated people are more than twice as likely to be reinfected as people who were vaccinated after contracting Covid. Brewer notes that people who have recovered from Omicron infection are likely to have better protection from BA.2 than people who have recovered from other Covid variants, or those who last more than four to six years ago months were vaccinated.
“But, [a] previous infection or vaccination still offers protection against serious illness and death,” he says.
Not all antibodies are “Covid-fighting” antibodies
dr Salman Khan, an infectious disease specialist at Lenox Hill Hospital in New York City, says it’s true that most people in the US have antibodies to Covid, either from a previous infection or from vaccination. But “not all of these are ‘Covid-fighting’ or neutralizing antibodies,” he says.
Sometimes, Khan says, “non-neutralizing antibodies” are produced in response to a pathogen. “These antibodies don’t bind sufficiently to the specific site of the pathogen to prevent it from continuing to cause infection,” he says. “In the case of SARS-CoV-2, this could have to do with mutations in the spike protein.”
These non-neutralizing antibodies work “almost like a GPS,” says Hannah Newman, director of infection prevention at Lenox Hill Hospital. They still attach themselves to the virus, but instead of working to stop the pathogen from spreading — like neutralizing antibodies do — they serve “as a localizer, signaling to other parts of the immune system that there’s a problem,” Newman says .
In other words, both types of antibodies are helpful to a degree – but testing positive for Covid antibodies is no guarantee your body will be able to fight off future Covid infection.
Nobody knows what the future will bring
If there’s one lesson to be learned from the Covid pandemic, it’s that no one can predict the future, says John P. Moore, professor of microbiology and immunology at Cornell University’s Weill Cornell Medicine.
“Because people want to believe the pandemic is over, they’re lowering their guard and acting less cautiously,” Moore says. But in reality nobody knows exactly what will happen tomorrow, next week or next month.
The seven-day average of daily new U.S. cases as of Monday is 30,662, according to data from Johns Hopkins University. That’s pretty low by pandemic standards, but it’s too early to tell if this trend is “real or just an outlier,” Moore says.
Moore also says it’s important to remember that the CDC’s antibody statistics are only an estimate. “That’s 95 percent of blood donors,” he says, noting that the study also doesn’t include anyone under the age of 16. “The question is: how representative of the general population are blood donors?”
Moore says he’s “not suggesting that everyone has to go into their basement and not come out again.” Rather, he advises, each person should monitor their own risk perception and make Covid-related decisions based on their own life and circumstances.
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