I just recovered from Omicron – how long does my immunity last?

If you recently recovered from an Omicron infection, do you now have free rein to do whatever you want without risk of reinfection? And if so, for how long?

Two main factors affect how well your acquired immunity after Omicron infection will protect you. 

First, your antibody levels. “If high levels of neutralising antibodies are elicited to Omicron following infection, then we would expect to see some level of protection against reinfection with Omicron, but this is likely to be short-lived,” says Professor Gilda Tachedjian, a virologist at the Burnet Institute and past president of the Australian Virology Society.

Generally, a more severe infection generates a higher level of antibodies than an asymptomatic infection, explains Professor Anthony Cunningham, an infectious diseases physician and clinical virologist at the University of Sydney. But when the level of neutralising antibodies begins to drop, your likelihood of reinfection rises.

It’s simply too early to know how long Omicron immunity will last, he says.

From vaccine studies, we know that antibody levels begin to drop after three to six months. A recent study published in The Lancet estimated that reinfection by SARS-CoV-2 under endemic conditions would likely occur between three months and five years after peak antibody response.

Almost certainly, Cunningham says, there will be a lot of individual variation, similar to what has been observed with previous strains. This variation depends on the severity of the disease you experienced, and whether you have had a vaccine.

The second factor: emerging variants. Our waning antibodies may not be able to target any new variants that come along. The Omicron variant, for example, largely evades immunity from past infection and vaccines. A recent report from Imperial College London estimates that the risk of reinfection with Omicron is 5.4 times greater than that of the Delta variant.

“The most likely outcome is that you won’t get re-infected with Omicron because the expectation is that the Omicron wave will decline, but then the greatest risk is that another strain comes along,” says Cunningham. “It all depends on what type of strain comes next.”

Even if you have had a recent Omicron infection, don’t throw your mask away, warns Cunningham: “The more virus circulates in the world, the more likely it is that we’ll see new strains.”

Although protection from reinfection might not last for long, experts think T-cells might come to the rescue.

While antibodies directly bind and neutralise virions, preventing an infection, T-cells activate once the infection is established. They target and kill virus-infected cells, helping to clear the infection and reduce its severity. This arm of the immune response tends to be broader than antibodies – and thus more likely to recognise variants, and to last longer, Tachedjian explains.

“Hopefully, you will be asymptomatic or have a less severe disease [the second time around].”