{{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} While I shivered during my mild period, I was optimistic that I would at least have several months of reprieve from isolation precautions and testing. But emerging evidence suggests the possibility of reinfection within a shorter time frame for newer subvariants. Experts have reduced the protective window of previous infection from 12 weeks to 28 days. This week, the governments of New South Wales, Western Australia and the Australian Capital Territory announced that those who have previously had COVID-19 will need to be tested after 28 days if they develop symptoms. If they are positive, they will be treated as new cases. Reinfection – testing positive for SARS-CoV-2 (the virus that causes COVID) after recovering from a previous infection – is ongoing. Reinfection accounted for 1% of all cases in the pre-Omicron period in England, but in recent weeks has accounted for more than 25% of daily cases there and 18% in New York. {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} We don’t have comparative data for Australia yet, but it will likely be a similar story given the appearance of the BA.4 and BA.5 Omicron sub-variants here. These are more easily transmitted and can cause unprecedented infection in people who have been previously vaccinated or infected. Understanding our risk of re-infection 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 individual protection 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 evasion characteristics of Omicron subvariants due to multiple novel mutations of the SARS-CoV2 spike protein. {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} Pre-Omicron, infection with a variant of COVID (Alpha, Beta, Delta) gave long-lasting cross-immunity. This also gave effective protection against symptomatic infection. However, that all changed with the emergence of the Omicron BA.1 subvariant in late 2021, with studies showing reduced cross-protection from previous infection that was associated with less robust antibody responses. Fast forward several months, and we can see even infection with early subvariants of Omicron (BA.1, BA.2) doesn’t necessarily protect us from their younger siblings (BA.4, BA.5). Our response to previous infection How our immune system dealt with previous COVID infection can affect how it deals with a future exposure. We know that immunosuppressed people are at increased risk of reinfection (or even relapse from a persistent infection). {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} The large UK Survey of COVID Infections shows that in the general population, people who report no symptoms or have lower virus concentrations on PCR smears with previous infection are more likely to be reinfected than those with symptoms or higher virus concentrations. This shows that when the body develops a stronger immune response to the first infection, it builds up defenses against re-infection. Perhaps a thin silver lining for those who shuddered, coughed and spluttered due to COVID! Vaccination status When the COVID vaccines were released in 2021, they provided excellent protection against severe illness (resulting in hospitalization or death) and symptomatic infection. Importantly, protection from serious disease is still in effect, due to our immune system’s responses against parts of the virus that have not mutated from the original strain. However, Omicron variants can infect humans even if they are vaccinated, as the variants have found ways to escape “neutralization” by the vaccine’s antibodies. {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} A new study shows that six months after the second dose of an mRNA vaccine (such as Pfizer and Moderna), antibody levels against all subvariants of Omicron are significantly reduced compared to the original (Wuhan) strain. That is, the vaccine’s ability to protect against infection with the subvariants declines faster than against the original strain of the virus. Antibody levels to all variants increased again two weeks after participants received a booster dose, 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 antibody levels in infected and vaccinated subjects. Again, gains were smaller for Omicron’s newer sub-variants. {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} Personal protection Most of the discussion lately has been about the immunogenicity of COVID. But don’t forget that the virus still needs to enter our respiratory tract to cause reinfection. SARS-CoV-2 is spread from person to person in the air by respiratory droplets and aerosols and by touching contaminated surfaces. We can stop transmission by doing all the things we’ve learned over the past two years – social distancing and wearing a mask when we can’t (preferably not a cloth one), washing our hands regularly, improving ventilation by opening windows and using an air purifier to poorly ventilated areas. And we can isolate ourselves when we are sick. A polluted 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 booster shots provide some modest protection. {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} While some (unlucky) individuals have been re-infected within a short period of time (less than 90 days), this appears to be unusual and related to the fact that they are young and mostly unvaccinated. Plans to market mRNA booster vaccines to target mutations of the Omicron spike protein offer the promise of regaining some immune control of these variants. That said, it will only be a matter of time before further mutations develop. The bottom line is that it will be difficult to overcome being infected or re-infected with a variant of COVID in the coming years. There’s not much we can do about the evolution of the virus or our own immune systems, but we can dramatically reduce the risk of serious infection to ourselves (and our loved ones) and disruption to our lives by being up-to-date on vaccinations and following simple infection control practices . {{^userSubscribed}} {{/userSubscribed}} {{^userSubscribed}} {{/userSubscribed}} By Ashwin Swaminathan, Australian National University This story has been published from a news agency feed without text modifications. Only the title has changed.
