While a previous SARS-CoV-2 infection can protect against a reinfection for an average of seven months, the immunity wanes afterwards. Repeated bouts of COVID-19 are harmful—even if the episodes are mild—because the long-term consequences add up for each additional infection, as demonstrated in a study of U.S. veterans. While veterans don’t necessarily reflect the broader public—because they tend to be older, white, and male—the research shows that patients who were reinfected with any SARS-CoV-2 variant are much more likely to develop chronic health issues like diabetes, kidney disease, organ failure, and even mental health problems.

Qureshi’s first infection was mild, with a fever that lasted a couple of days, aches, and cold symptoms, she recalls. “My major symptom was that I lost smell and taste.” But the most recent infection was disabling. She was bedridden for a week, could barely stand, and had severe cognitive impairment. “I couldn’t think straight,” says Qureshi. “The most recent one was really bad.”

With reinfections rising it is good news that the U.S. Food and Drug Administration approved Pfizer’s and Moderna’s new COVID-19 boosters on September 11. The preliminary data from Moderna, which has not yet been peer-reviewed and published, shows that the XBB.1.5 based booster, which could be available to the public as soon as this week generates ample levels of antibodies not only against the latest highly mutated Omicron BA.2.86 variant, but also against other currently circulating strains, EG.5.1 and FL.1.5.1.

After the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices met yesterday and voted in favor of the new shots, CDC director Mandy Cohen signed off on the panel’s recommendations. “CDC is now recommending updated COVID-19 vaccination for everyone six months and older to better protect you and your loved ones.”

It is recommended everyone complete their primary COVID series and stay up to date on the boosters. While vaccines and boosters may not block new or reinfections, they provide a strong protection against serious complications or hospitalization.

Soaring reinfection rates

The CDC defines a reinfection as when someone tests positive for SARS-CoV-2—the virus that causes COVID-19—on a PCR test 45 days after recovering from a previous confirmed infection. In the United States, about 2.7 percent of all reported COVID cases during the Delta variant surge in late 2021 were reinfections. But the problem became significantly worse when Omicron emerged, and its more infectious subvariants became dominant.

A CDC analysis of lab-confirmed, adult COVID cases between September 2021 and December 2022, found that reinfection rates jumped to 10.3 percent during the Omicron BA.1 wave; 12.5 percent when BA.2 was dominant; 20.6 percent during BA.4/BA.5; and 28.8 percent during the BQ.1/BQ.1.1. The good news is that a meta-analysis of 91 published studies showed that vaccination lowered the risk of getting reinfected, although vaccines became less efficient in preventing reinfections against Omicron variants.

But the numbers of reinfections are likely to be underestimated because not everyone who gets infected with SARS-CoV-2 gets sick enough to get tested. Since reinfection often generates somewhat milder symptoms, it is even more difficult to fully assess the true tally. Being a virologist, Qureshi frequently takes COVID tests when she suspects something is off, and that’s why she knows she has had frequent re-infections.

A Canadian study estimated that 40 percent of people who had antibodies in their blood—proof that they had been infected with SARS-CoV-2—had not experienced any symptoms in the previous six months and were unaware they had gotten the disease.

Studies from various other countries also suggest that reinfection rates can range from 5 percent to 15 percent. An analysis of COVID-19 cases in Serbia, for example, found that risk of getting reinfected has steadily increased during the pandemic, but it spiked after the arrival of Omicron variants in December 2022.

Who is most likely to get reinfected?

People who work in jobs with a lot of face-to-face contact, such as teachers and other school employees, healthcare professionals, and those who live in multigenerational households often have frequent recurrent COVID infections. For example, healthcare employees working in COVID-19 clinical units can have a four-fold higher risk of getting reinfected relative to those working in non-clinical units.

Studies show that the risk of someone getting COVID-19 are much higher among families with young children. In fact, over 70 percent of nearly 850,000 U.S. households might have caught COVID-19 through a child during the school year.

I now treat a lot of people with multiple COVID infections. A lot of them have risk factors like having young children in the school system.

Christine Micheel, like Qureshi, is also a mother of two young children. She first got COVID-19 in December 2020 just before vaccines became available. However, even after getting fully vaccinated and boosted, she ended up getting COVID-19 again in July 2022 during the BA.5 Omicron wave. Her son also got infected three times, while her daughter has caught it twice, although both children were fully vaccinated at the time.

Their symptoms were so minor, I think only I, as their mother, could have noticed them as unusual and given them a test.

With schools reopening amidst rising numbers of COVID-19 cases, children might unknowingly be spreading the disease to their households. How many kids have probably been walking around spreading COVID-19 with no one the wiser?

The antibodies against SARS-CoV-2 wane substantially within three months, especially in patients with less severe symptoms. However, immune response to a previous infection, or vaccine, can vary a lot between individuals.

Nobody is immune to this, ooner or later, you will get an infection.