How soon can you be reinfected with covid? | Canberra CityNews

Rapid Antigen Test.

How soon can you get covid again? Experts now say 28 days – but you can protect yourself, writes doctor ASHWIN SWAMINATHAN.

My extraordinary two-and-a-half year negative covid test came to a halt last week, after receiving a text confirming I was among the latest pandemic catches.

My case adds to the tilt of the third Omicron wave in seven months, currently rolling across Australia.

Shivering through my light fights, I optimistically thought that I would at least get a few months reprieve from the precautionary measures and isolation testing. But emerging evidence suggests the possibility of reinfection in a shorter timeframe for the newer subvariants.

Experts have reduced the window of protection from previous infections from 12 weeks to 28 days. This week, the NSW Western Australia government and the ACT all announced those with previous COVID-19 need to get tested after 28 days if they develop symptoms. If positive, they will be treated as new cases.

Re-infection – testing positive for SARS-CoV-2 (the virus that causes covid) after recovering from a previous infection – is on the rise. Re-infections accounted for 1 per cent of all cases in the pre-Omicron period in the UK, but in recent weeks accounted for more than 25 per cent of daily cases there and 18 per cent in New York City.

We don’t have Australian comparative data yet, but it’s likely to be a similar story, given the emergence of the BA.4 and BA.5 Omicron subvariants here. It is more easily transmitted and can cause breakthrough infections in those previously vaccinated or infected.

Understanding the risk of reinfection at the individual level is easier if we break it down into four main factors: virus, each person’s immune response to past infections, vaccination status, and personal protective measures. There’s not much we can do about the first two factors, but we can take action on the last two.

Virus

Much has been written about the immune system evading characteristics of the Omicron subvariance due to several novel mutations of the SARS-CoV2 spike protein.

Pre-Omicron, single-variant covid infection (Alpha, Beta, Delta) provides long-lasting cross-variant immunity. It also provides effective protection against symptomatic infections.

However, all that changed with the emergence of the Omicron BA.1 subvariant in late 2021, with studies showing decreased cross-protection from previous infection associated with a less robust antibody response.

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 past infections

How our immune system handles previous covid infections can affect how it negotiates future exposure.

We know individuals with suppressed immunity are at increased risk of reinfection (or indeed relapse from persistent infection).

The large UK Covid-19 Infection Survey showed that in the general population, people who reported no symptoms or had lower virus concentrations in their PCR swabs with previous infections were more likely to be reinfected than those who had symptoms or higher virus concentrations.

This suggests that when the body mounts a stronger immune response to the first infection, it builds up a defense against re-infection. Maybe a thin silver lining for those shivering, coughing and stuttering because of covid!

Vaccination status

When the covid vaccination rolls out in 2021, it provides excellent protection against severe illness (resulting in hospitalization or death) and symptomatic infection.

Importantly, protection from severe disease still applies, because of our immune system’s response to the unmutated parts of the virus from the original strain. But the Omicron variant can infect people even if they are vaccinated because the variant has found a way to avoid “neutralization” of the vaccine antibodies.

A new study showed six months after the second dose of mRNA vaccination (such as Pfizer and Moderna), antibody levels against all Omicron subvariants were greatly reduced compared to the original strain (Wuhan). This means that the vaccine’s ability to protect against subvariant infection decreases more rapidly than against the original strain.

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

Personal protection

Most of the discussion these days is about the ability to evade immunity from COVID. But don’t forget the virus still has to enter our respiratory tract to cause re-infection.

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

We can stop transmission by doing all the things we have been taught for the past two years – social distancing and wearing masks when we can’t (preferably not using cloth), washing our hands regularly, increasing ventilation by opening windows and using an air purifier to poorly ventilated room. And we can isolate ourselves when we are sick.

Reinfected future?

There is some recent data showing hope that reinfection may be common, but rarely associated with severe disease. It also shows booster shots providing simple protection.

While some (unlucky) individuals have been reinfected within a short period of time (less than 90 days), this does not appear to be common and is associated with a young age and most are not vaccinated.

The planned launch of an mRNA-boosting vaccine to target Omicron spike protein mutations offers promise for regaining some immunological control of this variant. That said, it is only a matter of time before further mutations develop.

The bottom line is that it will be difficult to outrun being infected or re-infected with this variant of covid in the years to come.

We can’t do much about the evolution of viruses or our own immune systems, but we can dramatically reduce the risk of severe infections to ourselves (and our loved ones) and disruptions to our lives, by staying up-to-date with vaccinations and following infection control practices. simple.

Ashwin Swaminathan, Senior Lecturer, Australian National University. This article is republished from The Conversation.

Australia braces for third and contagious wave of the Omicron

Who can be trusted?

In a world that is swirling and confusing, there has never been a more important time to support independent journalism in Canberra.

If you believe in our online work and want to uphold the power of an independent voice, I invite you to make a small contribution.

Every dollar of support is reinvested into our journalism to help keep citynews.com.au strong and free.

Become a supporter

Thank you,

Ian Meikle, editor

#reinfected #covid #Canberra #CityNews