Rapid antigen test.
When will you be able to have covid again soon? Experts now say 28 days, but you can protect yourself, writes Dr. ASHWIN SWAMINATHAN.
MY glorious two-and-a-half-year series of negative covid tests stopped last week after receiving a text message confirming it was among the latest catches of the pandemic.
My case adds to the rising slope of Omicron’s third wave in seven months, which is currently rolling through Australia.
As I trembled at my mild attack, I had thought optimistically that I would at least have a few months of rest from the precautions and isolation tests. But emerging evidence suggests the possibility of reinfection in a shorter period of time for newer subvariants.
Experts have reduced the window of protection from previous infection from 12 weeks to 28 days. This week, the governments of NSW Western Australia and ACT announced that those who have had covid before will have to take the test after 28 days if they show symptoms. If they are positive, they will be treated as new cases.
Reinfection, which has tested 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 cases in the pre-Omicron period in England, but in recent weeks accounted for more than 25% of daily cases there and 18% in New York City.
We do not yet have comparative data from Australia, but it will probably be a similar story, given the emergence of the Omicron BA.4 and BA.5 subvariants here. These are more easily transmitted and can cause advanced infections in people who have been vaccinated or previously infected.
Understanding our risk of reinfection on an individual level is easier if we break it down into four key factors: the virus, each person’s immune response to past infection, the state of vaccination, and personal protective measures. We can’t do much about the first two factors, but we can take action on the last two.
The virus
Much has been written about the immune system evading the characteristics of Omicron subvariants due to multiple new mutations in the SARS-CoV2 ear protein.
Pre-Omicron, infection with a variant of covid (Alpha, Beta, Delta) gave a long-lasting cross-immunity. This also offered effective protection against symptomatic infection.
However, all that changed with the advent of the Omicron BA.1 subvariant in late 2021, with studies showing reduced cross-protection from previous infection that was related to less robust antibody responses.
It progresses rapidly a few months, and we can see that even infection with early subvariants of Omicron (BA.1, BA.2) does not necessarily protect us from its younger siblings (BA.4, BA.5).
Our response to past infection
The way our immune system coped with previous covid infection may influence the way it negotiates future exposure.
We know that immunocompromised people have a higher risk of reinfection (or, in fact, relapse of a persistent infection).
The large UK covid infection survey shows that in the general population, people who report no symptoms or who have lower virus concentrations in their PCR swabs with their previous infection are more likely to be re-infected. I know that those with symptoms or higher viral concentrations.
This indicates that when the body develops a more robust immune response to the first infection, it builds defenses against reinfection. Perhaps a thin silver lining for those who trembled, coughed, and gasped for covid!
Vaccination status
When covid vaccines were implemented in 2021, they provided excellent protection against serious illness (which resulted in hospitalization or death) and symptomatic infections.
It is important to note that protection against serious diseases is still maintained, due to the responses of our immune system against the parts of the virus that have not mutated from the original strain. But Omicron variants can infect people even if they are vaccinated, as variants have found ways to escape the “neutralization” of vaccine antibodies.
A new study shows six months after the second dose of an mRNA vaccination (such as Pfizer and Moderna), antibody levels against all Omicron subvariants are markedly reduced compared to the original strain (Wuhan). That is, the ability of the vaccine to protect against infection with subvariants decreases more rapidly than against the original strain of the virus.
Antibody levels in all variants increased again two weeks after participants had a booster vaccine, but BA.4 and BA.5 showed the smallest incremental gains. Interestingly, in this study (and relevant to our highly immunized population), there were higher levels of antibodies in subjects who had been infected and vaccinated. Again, gains were lower for the newer Omicron subvariants.
Personal protection
Most of the discussion lately has been about the immune evasion capacity of covid. But don’t forget that the virus has yet to enter our respiratory tract to cause a reinfection.
SARS-CoV-2 is transmitted from person to person in the air by respiratory droplets and aerosols, and by touching contaminated surfaces.
We can interrupt the transmission by doing all the things we have been taught for the past two years: social distancing and wearing a mask when we can’t (preferably not clothes), washing our hands regularly, improving ventilation by opening windows, and using a purifier. of air for poorly ventilated spaces. And we can isolate ourselves when we are sick.
A reinfected future?
There are some promising recent data showing that while reinfection may be common, it is rarely associated with serious illness. It also shows that reinforcement shots provide modest protection.
Although some (unfortunate) individuals have been reinfected in a short period of time (less than 90 days), this seems uncommon and is related to being young and mostly unvaccinated.
Plans for the release of mRNA-enhancing vaccines to target Omicron spike protein mutations offer the promise of regaining some immune control of these variants. That said, it will only be a matter of time before more mutations develop.
The bottom line is that it will be difficult to overcome getting infected or reinfected with a covid variant in the coming years.
We can’t do much about the evolution of the virus or our own immune system, but we can drastically reduce the risk of serious infection in ourselves (and our loved ones) and the disruption of our lives, keeping us up to date. with vaccinations and following simple infection control practices.
Ashwin Swaminathan, Professor at the National University of Australia. This article is republished from The Conversation.
Australia prepares for Omicron’s third contagious wave
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