How long does COVID-19 immunity last?

21st July 2020: A recent study from King’s College London suggested that the immunity against COVID-19 might vanish in a couple of months. However, the truth is a bit more complicated and a little less dire.

Analyzing a study from the United Kingdom, the Guardian declared last week that ‘Immunity to COVID-19 Could Be Lost in Months.’ Forbes further accelerated the timeline: ‘Study: Immunity to Coronavirus May Fade Away Within Weeks.’ The San Fransisco Chronicle grimly reported: ‘With Coronavirus Antibodies Fading Fast, Vaccine Hopes Fade, Too.’

The researchers at King’s College London tested more than 90 COVID-19 patients repeatedly from March to June. Several weeks after infection, antibodies were abundant in their blood. However, two months later, the majority of these antibodies had disappeared.

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These results seemed very dire as it meant that our defense against COVID-19 disappear within a matter of a few weeks and the patients are at risk of contracting the disease again. In such a situation, herd immunity is out of the question, unfortunately meaning that vaccines working on the basis of antibody response would be useless after a few months.

 

Acquired immunity is cellular memory, meaning when our body fights off an infection, our immune system remembers how to defeat it again. The entire point of a vaccination is to teach the immune system how to fight the disease without exposing it to the full virus.

This is what made this recent study look so dreadful. It exposed that the number of certain active antibodies, called neutralizing antibodies, declined significantly between tests, especially in patients with mild or no symptoms.

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Antibody levels are a substitute for the immune system’s memory. If they decrease rapidly, this might indicate that our immune system is unable to remember how to fight COVID-19 for more than a couple of months at a time, leading us to consequently start from scratch with every new exposure. None of the COVID-19 researchers are rooting for antibody levels to decline so quickly.

However scary the results and consequences seem, scientists have agreed on three reasons to still be hopeful despite the situation.

Firstly, they explained that the human immune system is very complicated and the KCL study has only researched on one part of it. When a new pathogen enters the body, our adaptive immune system stimulates various B cells, which produce antibodies, and T cells.

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To explain this in easier words, the B cells’ antibodies intercept and bind to the invading molecules, whilst the killer T cells find and destroy infected cells. Analyzing an immune response without accounting for T cells is similar to inventorying a national air force but leaving out the bomber jets.

In the case of COVID-19, those bomber jets could make the biggest difference. A large amount of evidence indicates that T cells provide the strongest and longest-lasting immunity to COVID-19—but the KCL study didn’t measure them at all.

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Eric Topol, a cardiologist and the founder and director of the Scripps Research facility, explained that ‘To look at just one part of the immune response is woefully incomplete, especially if many COVID patients rely more on T cells.’ He referred to a study from France’s Strasbourg University Hospital, which found that some people recovering from COVID-19 showed strong T-cell responses without detectable antibodies. “There is a chance that if a similar longitudinal study looked at T-cell response, the outcome would be far more optimistic,” he shared.

Shane Crotty, a virologist at the La Jolla Institute for Immunology, shared that ‘I was definitely very worried when I saw the headlines,’ he further continued saying, ‘But then I looked at the data. And actually, looking at the data, I feel okay about it.’

Secondly, the virologist Shane Crotty elaborated that although the decline in antibodies is alarming, it is not catastrophic, ‘It’s not unusual to have fading antibody response after several months,” he said. “The drop-off isn’t that surprising. When you look at something like the smallpox vaccine, you see the antibody response is down about 75 percent after six months. But that’s a vaccine that works for decades. We need a study like this to look at COVID patients six months after infection to really know what we’re dealing with.’

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Thirdly, even low levels of antibodies can prove to be enough to defeat the COVID-19 virus, as they can peak the immune response later. Pamela Bjorkman, a biochemist at the California Institute of Technology, explained, ‘t’s possible that previously-infected people could utilize [immunological memory] responses to produce new antibodies in case they are exposed to SARS-CoV-2 again.’ She continued, ‘So I would not conclude yet that people infected with SARS-CoV-2 are not protected from another infection.’

The scary KCL study might initially seem to describe a forgetful antibody response. But, primed by the reappearance of COVID-19, our immune system is most likely to snap back and bring forth a powerful defense.

Beyond these three caveats to the panic-stricken headlines, various other developments give us a reason to be hopeful that the pandemic won’t last forever. Vaccine research is continuing to accelerate ahead at a fast pace.

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Numerous studies on monkeys, whose immune systems are as close to ours as that of any animal, have been promising, depicting a strong and lasting immune response. Recently, a paper shows that 17 years after SARS first struck East Asia, several patients have “long-lasting T cell immunity” that might even be helping them fight COVID-19, a.k.a SARS-2.

The task of understanding COVID-19 is an unprecedented global effort, and each study is a small part of extensive research. News consumers feeling jerked around by headlines that are alternatively optimistic and devastating should remember this: We are living in the midst of a pandemic and learning more every week about this novel coronavirus, but the immune system is a big, complicated place.

A single study focusing only on one part of this big, complicated place should not convince you that a vaccine is doomed to fail or that this pandemic will be with us forever.

Stay tuned to Baaghi TV for more updates.

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