‘But I just had Covid’ – Why Omicron is driving up reinfection rate

Likelihood of reinfection has increased with the latest variant of concern, says Dr Gerald Barry

Andrew Byrne (25) contracted Covid-19 for the first time in November but had very mild symptoms and thought he had "cheated Covid". A month and a half later, he tested positive for the virus again.

The rapid spread of the highly transmissible Omicron variant throughout the State has had an impact on not just daily case counts, but also the number of re-infections.

In Byrne’s case, his first experience with the virus largely felt like a bad head cold. However, the second time “it was a much worse dose”.

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“I woke up with really bad pain, chills, I couldn’t get out of the bed. Bright lights gave me a migraine. Fatigue was setting in – I was finding it hard to stay awake when watching TV and there was a general feeling of tiredness in my muscles and my body,” he said.


After several days, Byrne said the symptoms eased and returned to what he described as head cold-type symptoms.

Byrne, who had the one-shot Janssen vaccine, said he was “really surprised” when he contracted Covid again, as it was only six weeks after his initial dose.

“I thought I’d be okay for at least three months,” he added.

Dr Gerald Barry, a virologist at UCD, said Covid reinfection has always been possible, but the likelihood of it has increased with the latest variant of concern.

A study from Imperial College London found the risk of reinfection with Omicron was 5.4 times that of Delta.

Case volumes

In Ireland, the Health Protection Surveillance Centre (HPSC) said it could not provide figures for the number of Covid reinfections in the State, as a result of the current Covid-19 case volumes.

Barry said: “The idea that if you’ve had an infection previously that you’re immune or protected from a new infection, that’s just not the reality with this virus.”

The body creates memories of previous infections, which then trigger a quick antibody response if exposed to the same virus again, he explained.

However, as a virus mutates, the body becomes unable to recognise it as quickly as it previously would have, allowing the person to become infected.

“If you’ve had an infection previously, you could be exposed to the same virus a lot, and if the antibodies are still high in your body within weeks or months post that initial infection, then, although you’ll be exposed to it, it’s very unlikely the virus will take hold,” he said.

You do build up a tolerance, I think. It wasn't that bad at all the second time. Waiting it out was the biggest inconvenience

“But if you have a new variant that your body hasn’t seen before, then the virus has a much higher chance of taking hold, particularly in your upper respiratory tract, and you might see symptoms of infection.”

Reinfection is not just a risk with the Omicron variant, either, according to Dr Barry, who said he had heard of people contracting Delta more than once.

Dominant variant

Linda Coogan Byrne contracted Covid-19 in January 2021 and again in the summer of that year, a time during which Alpha was the most dominant variant in circulation.

“I was absolutely floored,” Coogan Byrne said. “My chest was really sore. My taste and smell went away and it took about six weeks to come back. And there was brain fog too.”

However, the second time, the most severe symptom experienced was night sweats, a difference Coogan Byrne attributed to the previous infection, as well as having been fully vaccinated by that time.

“You do build up a tolerance, I think. It wasn’t that bad at all the second time. Waiting it out was the biggest inconvenience.”

Milder symptoms in subsequent infections is common, according to Dr Barry, particularly if the second infection is with the Omicron variant.

This is both a result of the antibodies from the previous infection, and the early indications that Omicron causes less severe infection, he said.

Considerably milder

That was the case for Helen Whelan, whose symptoms were considerably milder when she contracted the virus the second time in early January, despite not yet being vaccinated on either occasion.

When Whelan first contracted it in September 2020, she had a headache, sore sinuses and a cold, spending the 10 days “pretty much in bed with no energy and sleeping all the time”.

The second time has been much more manageable. “I’d describe it as a bad head cold more than anything but I haven’t missed a day of work.”

Craig Dwyer, who contracted Covid-19 twice in just over seven weeks, had a similar experience.

The first time he had it, in November, he had extreme fatigue, and the symptoms of a head cold and sinus infection. The second time, last week, it was only a scratchy throat.

“I’m not feeling too bad at all this time,” he said. “I was hoping that because I had it already, I would have some sort of immunity, but I guess I didn’t.”

Dwyer (32) had the one-shot Janssen vaccine, and now must wait three months before he is eligible for a booster for additional protection.

“I’m probably a little bit more nervous now than I was after contracting it the first time, because I thought I had a bit of immunity then.

“I don’t necessarily feel as safe or protected. I’m really hoping I can just go the three months so I can get a booster.”