“Reinfection is common and increases your risk of bad outcomes,” Professor Raina MacIntyre, head of the Kirby Institute’s biosecurity program, wrote in the Saturday Paper.
“Being infected with Omicron BA.1 earlier in 2022 does not give you much protection against the newer variants.”
But others remain skeptical about the studies’ results.
Does infection with Omicron offer protection against future infection?
In June, a UK-based research team caused a stir with its surprise finding, published in the journal Sciencethat getting infected with Omicron seemed to provide little protection against reinfection with Omicron.
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This might be a case of “immune imprinting”, the researchers suggested: the immune system remembering the first version of the virus it saw and building antibodies to that older version each time it encountered a new variant.
But science is accumulative: many studies over time build an accurate picture of what’s going on.
the Science paper studied antibodies in a test tube; data from the real-world is more optimistic.
A paper from Qatar suggests Omicron infections are close to 80 per cent effective at preventing infection with Omicron subvariants BA.4 and BA.5. Studies from Denmark and Portugal come to similar conclusions.
Does each reinfection increase the risk of bad outcomes?
Also in June, a team led by Washington University’s Ziyad Al-Aly uploaded its paper based on a large healthcare database operated by the US Department of Veterans Affairs, which covers US military veterans. They extracted healthcare data for people who had been infected and reinfected, and compared that with veterans who had never been infected.
Compared with those who had been infected once, veterans who had been reinfected were three times more likely to be hospitalized and twice as likely to be dead. They were more than twice as likely to have heart or blood problems, fatigue or mental health issues. As people had more reinfections, their health problems increased.
Professor Rhonda Stuart at the vaccination hub at Monash Medical Centre.
Based on this paper, we should be doing all we can to avoid reinfection, said Professor Rhonda Stuart, director of epidemiology at Monash Health.
“If you have a chance of getting long COVID from your first infection, it would seem to make sense that you have the same chance the next time you get COVID,” she said.
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“In the end, the message is, if you’ve had COVID, you don’t want to get it again.”
If reinfection is worse than primary infection, this would be an unusual feature of the virus. In many other respiratory viruses, “reinfection typically results in a milder illness with a shorter duration”, said Dr Gemma Saravanos, a respiratory infection researcher at the University of Sydney.
The paper has not yet been peer reviewed or published in a scientific journal – meaning it needs to be interpreted with caution.
Other scientists identified possible biases in the paper that may cloud the results.
The study used healthcare records, meaning people had to be sick enough to use healthcare. That means it might have missed people who had asymptomatic reinfections, or cases so mild they did not get tested. By oversampling people who got very sick after reinfection, the study could make the effect of reinfection seem worse. “I think there are fair concerns about sampling bias,” said Assistant Professor Saskia Popescu from the US-based George Mason University’s biodefence program. “Especially in this case, as they used a population … which may be more likely to have existing health challenges and co-morbidities.”
The study also compared people infected with the original strain of the coronavirus and those reinfected with the Delta variant – which is known to be more severe.
Professor Tony Blakely.Credit: Supplied
Based on that, “I would confidently predict that the risk of serious symptoms on a reinfection – compared with first infection, and for hypothetically same virus – is less,” said University of Melbourne epidemiologist Professor Tony Blakely. “But time will tell.”
Other studies come to different conclusions than the June papers. A study published in the Journal of Infection in April, looking at 13,960 reinfections in Britain, found people were 61 per cent less likely to die from a reinfection compared with an initial infection. Rates of hospitalization were also dramatically lower. Similar data has been published from Serbia and Qatar.
For Efron, having experienced none of the effects of long COVID, it was the reassurance of knowing what lay ahead that made the second infection easier than the first.
“I just remember the first time feeling tightness of breathing and found that alarming and a bit uncomfortable. So I think the second time actually was a little bit better.”
Liam Mannix’s Examine newsletter explains and analyzes science with a rigorous focus on the evidence. Sign up to get it each week.