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Do you have COVID again? Your symptoms may be milder, but this will not always be the case

So you start to feel uncomfortable. Your throat hurts, your head hurts, you feel tired and you have developed a cough.

You recently had COVID, but as we now know, it’s possible to get infected again.

But how sick will you get the second time?

While your symptoms are likely to be less severe, in some cases they can be worse. Here’s what we know so far.

Post COVID you don’t need to test for 12 weeks

Current guidelines define you as a “resolved case” for 12 weeks after the end of the COVID isolation. If you develop COVID-like symptoms during those 12 weeks, you do not need to get tested.

The science behind this 12-week time frame is evolving. The original idea was that if you recovered from COVID and have a healthy immune system, you developed immunity to reinfection. And that protects you for at least 12 weeks.

With increasing case numbers in Australia, reports of reinfections are also increasing. And it’s likely that reinfection will occur sooner than we first thought.

What is happening in our body?

For a person to be able to fight off reinfection with a virus, they must have developed a protective immune response.

Two main factors determine whether a person displays a protective immune response:

1) how long a person’s immune memory lasts

2) how well that store detects the virus or a slightly different virus.

Immune memory is made up of many critical parts, each of which plays a role in your immunity’s protective army. The biggest players in protective immunity memory are your B cells (which mature to make antibodies) and your T cells (which destroy virus-infected host cells).

So far, the evidence suggests that immune memory for SARS-CoV-2, the virus that causes COVID, lasts for months or even years when it comes to B cells and the antibodies they produce.

Similarly, current evidence shows that T cell memory can last over a year.

This means that the immune memory for SARS-CoV-2 in a healthy person lasts for a year against reinfection with the exact same virus.

SARS-CoV-2 animation.
The immune memory of SARS-CoV-2 can last for months or even years.

So why the reinfections?

A clear explanation for reinfection is that the virus mutates. SARS-CoV-2 replicates rapidly, making replication errors in the process. We refer to these errors as mutations. Over time, the mutations accumulate and a new subvariant is born.

Since the beginning of the pandemic, we’ve seen the parental Wuhan strain mutate into Alpha, Beta, Delta and now Omicron.

Read more: Why are there so many new Omicron subvariants like BA.4 and BA.5? Will I get infected again? Does the virus mutate faster?

Current theory is that immunity to one variant may not provide adequate protection from another.

Previous data suggests that the Omicron variant is better at immune escape than its predecessors. This means that Omicron “escapes” the immune memory created by SARS-CoV-2 infections from other variants such as Delta, Beta or Alpha.

New data now shows that subvariants of Omicron can also escape the immunity of an earlier Omicron variant. This means that a person can potentially get Omicron reinfection.

A small study from Denmark, which was still being reviewed by experts, showed that unvaccinated people who were initially infected with Omicron BA.1 could be reinfected with Omicron BA.2. Despite this finding, the study also concluded that reinfection rates were low and therefore rare.

As winter approaches and case numbers increase, we are also seeing the emergence of new subvariants such as BA.4 and BA.5. Early evidence shows that these new subvariants are even better at evading immune memory than the parent BA.1 omicron.

Read more: BA.2 is like Omicron’s sister. Here’s what we know about it so far

What about the heaviness?

For those who do get reinfection, the severity of the disease appears to be milder and less likely to result in hospitalization. This is likely because the immune memory can recognize at least part of the re-infecting virus.

However, it is difficult to measure the severity of the disease at the population level. A systematic review of case studies found that while some secondary infections were milder, this was not the case in all cases. Some reinfections resulted in worse outcomes, including death. (During this study period, one of the original strains, B.1, caused most primary infections, with reinfections being caused by alpha or beta variants.)

But although Omicron appears to cause more reinfections than other variants, there isn’t enough robust data to draw firm conclusions about the severity of reinfection with Omicron or other variants.

What we do know for sure is that we need more data from more people to say reinfection is less severe.

We also know from several studies that a vaccination protects against re-infection, even in people who are already infected and who then receive subsequent vaccinations.

Intensive care physicians treat a patient with COVID.
Some reinfections cause serious illness.

Another reason to recharge

A recent study, pending peer review, found that immunity to the Omicron BA.1 variant drops 7.5-fold with the new Omicron BA.4 and BA.5 variants. This means that the antibodies you produce when you have BA.1 infection, which can recognize and neutralize the BA.1 virus, are 7.5 times less able to recognize and neutralize BA.4 and BA.5 than BA. 1.

This study also found that vaccination plus natural exposure to Omicron BA.1 provides five-fold greater protection to Omicron BA.4 and BA.5 than immunity from natural exposure to BA.1 alone.

Read more: COVID Reinfections: Are They Milder and Do They Boost Immunity?

The data also show that the strongest protective immunity comes from a mix of triple vaccination and natural infection.

Another study found that this type of hybrid immunity provided better protection against both reinfection and hospitalization than natural immunity alone, underscoring the importance of vaccination and vaccine boosters.

So the question remains: if our immune memory lasts a year but is too specific to recognize the new variants, do we need a new vaccine every year? We will see.

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