How soon can I get Covid again? Experts now say 28 days! † Health


My glorious two-and-a-half-year run of negative COVID tests came to a shuddering halt last week, after I received a text message confirming I was among the last catch of the pandemic. My case contributes to the rising slope of the third Omicron wave in seven months, which is currently rolling through Australia. (Also Read: Had Covid At Christmas? You Could Get It Again Now)



As I shivered by my mild attack, I had optimistically thought that I would have at least a few months’ delay from isolation measures and testing. But emerging evidence suggests the possibility of reinfection within a shorter time frame for newer subvariants.

Experts have reduced the protective period of previous infection from 12 weeks to 28 days. This week, the governments of New South Wales, Western Australia and Australian Capital Territory all announced that those who have previously had COVID should test after 28 days if they experience symptoms. If they are positive, they are treated as new cases.

Reinfection – testing positive for SARS-CoV-2 (the virus that causes COVID) after recovering from a previous infection – is on the rise. Reinfection accounted for 1% of all pre-Omicron cases in England, but in recent weeks it accounted for more than 25% of daily cases there and 18% in New York City.



We don’t have any comparative Australian data yet, but it will likely be a similar story given the emergence of BA.4 and BA.5 Omicron sub-variants here. These are more easily transmitted and can cause breakthrough infection in those who have been previously vaccinated or infected.

Understanding our risk of reinfection at an individual level is easier if we break it down into four key factors: the virus, each person’s immune response to previous infection, vaccination status, and personal protective measures. We can’t do much about the first two factors, but we can take action about the last two.

The virus

Much has been written about the immune system evading the features of the Omicron subvariants due to multiple novel mutations of the SARS-CoV2 spike protein.



Pre-Omicron, infection with one variant of COVID (Alpha, Beta, Delta) conferred long-lasting cross-variant immunity. This also provided effective protection against symptomatic infection.

However, that all changed with the emergence of the Omicron BA.1 subvariant in late 2021, with studies demonstrating reduced cross-protection against previous infection associated with less robust antibody responses.

Fast forward a few months, and we can see that even infection with early Omicron subvariants (BA.1, BA.2) does not necessarily protect us from their newer siblings (BA.4, BA.5).

Our response to previous infection

How our immune system coped with the previous COVID infection may affect how it negotiates a future exposure.

We know that immune-suppressed individuals are at increased risk of reinfection (or even relapse from an ongoing infection).



The large UK COVID infection survey shows that in the general population, people who report no symptoms or have lower virus concentrations on their PCR swabs with their previous infection are more likely to be re-infected than people with symptoms or higher viral concentrations .

This indicates that when the body mounts a stronger immune response to the initial infection, it builds defenses against reinfection. Maybe a silver lining for those who shivered, coughed and sputtered from COVID!

Vaccination status

When COVID vaccinations were rolled out in 2021, they provided excellent protection against serious illness (resulting in hospitalization or death) as well as symptomatic infection.

Importantly, protection against serious disease still applies, due to our immune system’s responses to the parts of the virus that have not mutated from the original strain. But Omicron variants can infect humans even if they have been vaccinated, because the variants have found ways to escape “neutralization” of vaccine antibodies.



A new study shows that six months after the second dose of an mRNA vaccination (such as Pfizer and Moderna), antibody levels against all Omicron subvariants are significantly reduced compared to the original (Wuhan) strain. That is, the ability of the vaccine to protect against infection with the subvariants declines more rapidly than against the parent strain of the virus.

Antibody levels in all variants rose again two weeks after the participants received a booster injection, but BA.4 and BA.5 showed the smallest incremental gain. Interestingly, in this study (and relevant to our highly immunized population) there were higher antibody levels in subjects who were both infected and vaccinated. Again, the gain was smaller for the newer Omicron sub-variants.



Personal protection

Most of the discussion lately has been about the immune-evasive potential of COVID. But remember, the virus still has to get into our respiratory tract to cause reinfection.

SARS-CoV-2 is spread from person to person in the air through respiratory droplets and aerosols and by touching contaminated surfaces.

We can disrupt transmission by doing all the things we’ve learned over the past two years: social distancing and wearing a mask if we can’t (preferably not a cloth), washing our hands regularly, improving ventilation by opening windows and an air purifier for poorly ventilated areas. And we can isolate when we are sick.

A recontaminated future?

There is some hopeful recent data showing that while reinfection is commonplace, it is rarely associated with serious illness. It also shows that booster shots offer modest protection.



While some (unlucky) individuals are re-infected within a short period of time (less than 90 days), this seems unusual and related to being young and mostly unvaccinated.

Plans to roll out mRNA booster vaccines to address the Omicron spike protein mutations offer promise of regaining some immunological control over these variants. That said, it will only be a matter of time before further mutations develop.

The bottom line is that in the coming years it will be difficult to become infected or re-infected with a COVID variant.

There’s not much we can do about the evolution of the virus or our own immune system, but we can dramatically reduce the risk of serious infection in ourselves (and our loved ones) and disruption to our lives by staying up to date with vaccinations and following simple infection control practices .



By Ashwin Swaminathan, Australian National University

This story was published from a news agency feed with no text changes. Only the headline has been changed.

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