LOS ANGELES — Emerging evidence suggests that catching the coronavirus a second time can heighten long-term health risks, a worrisome development as the circulation of increasingly contagious omicron subvariants leads to greater numbers of Californians being reinfected.
Earlier in the pandemic, it was assumed that getting infected afforded some degree of lasting protection, for perhaps a few months.
As the coronavirus mutates, though, that's no longer a given. And each individual infection carries the risk not only for acute illness but the potential to develop long COVID.
"The additive risk is really not trivial, not insignificant. It's really substantial," said Dr. Ziyad Al-Aly, clinical epidemiologist at Washington University in St. Louis and chief of research and development at the Veterans Affairs St. Louis Healthcare System.
According to a preprint study examining U.S. veterans, of which Al-Aly was the lead author, getting infected twice or more "contributes to additional risks of all-cause mortality, hospitalization and adverse health outcomes" in various organ systems, and can additionally worsen risk for diabetes, fatigue and mental health disorders.
"Reinfection absolutely adds risk," Al-Aly said. The study suggested that, compared with those infected only once, individuals who caught the coronavirus a second time were at 2½ times greater risk of developing heart or lung disease and blood clotting issues. Subsequent infections also were associated with a higher risk of potentially serious health problems, as well as death from COVID-19.
It's possible that a repeat coronavirus infection will leave someone just fine, which is what happens to most people, Al-Aly said. "But you might be one of the unlucky ones and … get some really serious health problem with an infection."
Los Angeles County Public Health Director Barbara Ferrer recently cited Al-Aly's pre-print study as rationale for wearing masks in indoor public settings to avoid reinfection.
"They also saw that those with repeat infections had a higher risk of gastrointestinal, kidney, mental health, musculoskeletal and neurologic disorders, as well as diabetes," Ferrer said of the study. "Moreover, the risk of developing a long-term health problem increased further with each reinfection. The risk of having long-term health conditions was three times higher for those infected compared to those who were uninfected."
Older viruses, such as those that cause measles and chickenpox, are quite stable — meaning that the vaccinations are highly effective and surviving either illness typically confers lifelong immunity.
Not so with the coronavirus, which has mutated wildly since the pandemic began. Someone who got infected with the variant that dominated California in late 2020, for instance, was vulnerable to catching the delta variant the following summer. And those who survived delta faced the risk of catching the later omicron variant.
But the reinfection landscape has been upended even further as California has been walloped with a family of increasingly transmissible omicron subvariants. The most recent of those, BA.5, has shown particular proficiency for reinfection — with the ability to target even those who survived an earlier omicron case mere weeks before.
"This concept of building immunity, it really only works if you're encountering the same beast again and again and again," Al-Aly said. But in the world of COVID-19, BA.5 is actually a "very different beast" than earlier variants.
It's possible that the acute phase of a second bout of COVID-19 could be milder than the first. But a subsequent attack can still leave more extensive cumulative damage to the body than if there had been only one infection.
Think of coronavirus infections like earthquake sequences: It's possible an aftershock could be less severe than the first temblor but cumulatively could add more damage. And just because your home is still standing after one quake doesn't mean you shouldn't explore ways to make it seismically safer.
"Part of the reason why things, for many people, feel like they're not so bad right now is because we are being very aggressive in countering the virus with vaccines, with treatments," Dr. Ashish Jha, the White House COVID-19 response coordinator, said during a healthcare summit hosted by the Hill. "If we took our foot off the pedal, we're going to see this virus come back in a way that's much more dangerous. So we've got to stay on that front footing and continue fighting this thing."
As it relates specifically to long COVID — a condition in which symptoms can persist months or even years after an initial infection — getting vaccinated and boosted likely reduces risk, but studies differ as to the degree of protection.
"I think having some preexisting immunity — whether it's natural or from a vaccine — appears to reduce your risk of long COVID, but it's still there. It's not zero," said Dr. Steven Deeks, a professor of medicine at UC San Francisco and principal investigator of the Long-term Impact of Infection With Novel Coronavirus, or LIINC, study.
Another report, observing triple-vaccinated Italian healthcare workers who weren't hospitalized for COVID-19, found that two or three doses of vaccine were associated with a lower prevalence of long COVID.
A separate report suggested that even adults who had received a booster dose still have to consider the risk of long COVID. A British report said that, during the initial omicron wave, about 1 in every 25 triple-vaccinated adults self-reported having long COVID three to four months after their first infection.
Still, some clinicians say that long COVID sufferers tend to be either unvaccinated or missing their boosters.
"The number of patients I'm seeing who were vaccinated and boosted who are coming in with long COVID is very low," said Dr. Nisha Viswanathan, director of the UCLA Health Long COVID Program.
Long COVID also doesn't prevent you from becoming infected with the coronavirus again. Viswanathan said she's had patients who have seen their long COVID symptoms improve, then get sickened with another bout of COVID-19, and then see long COVID signs return.
The best way to prevent long COVID is to not get COVID-19. Many officials and experts cite non-pharmaceutical interventions such as masking as key tools, since vaccinations reduce, but do not entirely eliminate, the risk.
"Masking is not a terrible thing to ask of people, especially in probably the places that are the most crowded, and the places that maybe are the highest risk of transmission," Viswanathan said. Taking activities outside is also safer than being unmasked indoors.
Some of Viswanathan's patients have downplayed the risk of COVID-19, commenting how it's become a mild illness, and adding they don't see the point of taking precautions. But, she said, better knowledge about long COVID and its disabling effects would help people understand the importance of masking and getting vaccinated and boosted.
A UCLA study published in the Journal of General Internal Medicine, of which Viswanathan was a co-author, found that of 1,038 patients with symptomatic COVID-19 between April 2020 and February 2021, nearly 30% developed long COVID. The most common symptoms were fatigue and shortness of breath among hospitalized patients.
While many are weary of COVID-19 preventive measures after nearly two and a half years, they remain important, said Dr. Anne Foster, vice president and chief clinical strategy officer for the University of California Health system.
The burden of long COVID following this wave is unknown. The official case tallies are likely vast undercounts, given that so many at-home tests are being used, and that could suggest that the burden of long COVID in subsequent months will be hard to predict, Foster said.
"I know everyone has moved on and people are going back to the way things were, and I sort of get it," Deeks said. "But people do need to be aware that there is this additional risk that's not going away and they might adjust their lives accordingly.
"But everyone's going to figure this out on their own."