Reinfection risk: Omicron appears to produce shorter-lived immunity, experts say

If you still haven’t been infected with COVID-19, the highly transmissible Omicron variant and BA.2 subvariant probably have you thinking you’re next in line.

But amid a sixth wave of infections, even those who have already caught the virus and recovered are wondering when reinfection could come knocking.

“It is possible to re-develop COVID after having recovered from it fairly recently,” Dr. Brian Conway, president and medical director of Vancouver Infectious Diseases Centre, told Global over Zoom.

A Queen’s University professor defines “recently” as three months following infection —  though it seems one sneaky variant has sprung up to test that interval.

“Before Omicron came along, we did not see people getting any kind of reinfection until about 90 days had passed. With Omicron, that interval seems to be a little bit shorter — it’s about 60 days,” said Dr. Gerald Evans, chair of the Division of Infectious Diseases.

It’s still very uncommon for people to test positive within that timeframe, said Evans.

In fact, York University immunologist Ali Abdul-Sater told Global most healthy, vaccinated individuals see their antibody levels begin to drop after four to six months. However, data from recent surges in the U.K. and Denmark shows infection within a 60-day window is still a possibility.

Overall, all three health professionals say it’s very difficult to determine the length of immunity a person has following an infection.

Factors like age, immunization status and the severity of an individual’s immune response after they caught COVID-19 can dictate their risk for reinfection, said Abul-Sater.

“Individuals who are either immunocompromised or individuals older than 65 have less of a robust immune response,” he said.

If you got really sick after catching COVID-19, Abdul-Sater said you may develop stronger immunity than someone who got mildly ill following infection.

Double-vaxxed and then got infected? You may develop a “hybrid immunity,” said Evans, which could last longer than immunity from a vaccine alone or an infection alone. And if you’re vaccinated, got infected and then got a booster shot, that may extend the immunity even longer, according to Abdul-Sater.

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Even more interesting? Evans and Abdul-Sater say the type of variant you catch may also affect your probability of reinfection.

Those who caught Delta appear to develop periodical immunity from another Delta infection and from all variants that have appeared prior.

But because Omicron has a different makeup than its predecessors, Evans said getting infected with the variant may only protect you briefly from another Omicron infection, yet may leave you vulnerable to all the other variants, including its subtype BA.2.

All the experts stress this is not something that individuals should go about and test. If you’re thinking you’re invincible after catching COVID-19, Abdul-Sater says the sixth wave is proof that the public should not get too comfortable right now, especially with the emergence of new variants.

“If you’ve recovered, please don’t consider yourself immune still. Follow the rules. Wash your hands. Be mindful of risky situations with large numbers of people,” said Conway.

Another reason to remain cautious? Children are also at risk of reinfection, says McGill University’s Dr. Bruce Mazer – as pediatric cases and hospitalizations are on the rise in Quebec and Ontario.

“Children’s immune systems are usually very similar to adults’, especially over age five,” said the professor of pediatrics and associate scientific director of the COVID-19 Immunity Task Force.

“In the United States and in other countries, they’re giving children the third dose six months after their second dose.”

Mazer stresses that no matter the perceived timeframe of your immunity, protection from a vaccine is way more robust than the protection produced from an infection.

When vaccines were first being rolled out, “there was hope that natural immunity would equal vaccine immunity,” said Conway, but that turned out to not be the case at all.

Even though vaccines were never a foolproof shield against COVID-19, according to Evans and Mazer, they do protect you from getting severely ill — something they say post-infection immunity doesn’t.

This is why the health professionals are urging the public to get caught up on their vaccines and boosters. The National Advisory Committee on Immunization (NACI) recommends non-immunocompromised individuals get their shot eight weeks after a COVID-19 infection.