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What does COVID-19 immunity mean, and how long does it last?

Almost a year has passed, and the world is still battling the coronavirus. Many lost their lives while others managed to survive the lethal virus. However, even as scientists are pooling most of their resources to raise above this health crisis, there are still many unknown factors. Thus, it is still unclear whether we could ever reach herd immunity without a vaccine or a high death toll.

Herd immunity

For the past couple of months, people hoped that herd immunity could provide some sort of solution for this health crisis. Alas, the theory of herd immunity prevailing against the current pandemic is still a topic of debate for many scientists and experts. Herd immunity is when enough people are immune to a pathogen to slow its spread. Furthermore, experts estimate that around 40 to 60 percent of a population would need to be infected to reach it. Thus, herd immunity isn’t exactly a solution as much as a slim chance. It also puts the entire population at risk of significant illness and death.

Nonetheless, many researchers are urging governments to reach herd immunity without a vaccine. They believe that allowing COVID-19 to spread among those at low risk while protecting vulnerable populations is the best solution. In a way, this is exactly what most governments are aiming for even though they might not label the approach.

However, since SARS-CoV-2 is a rather new and complicated virus, scientists can’t say how long a person will be protected after they’ve recovered from an infection. Therefore, if the calculation were wrong and the immunity wanes quickly, the world will face a recurrent outbreak. The results might even end up being worse than the current situation.

What is immunity?

Scientists have defined immunity as the “ resistance to a disease gained through the immune system’s exposure to it, either by infection or through vaccination”. On the other hand, gaining immunity doesn’t always equal complete protection from the said virus. There are many factors that determine the level of “protection” immunity can provide.

The immune system has two ways to provide lasting protection. One way is the T cells. Such cells remember the pathogen and trigger a rapid response when provoked. The other one is through B cells. Unlike T cells, B cells produce antibodies which are proteins the body makes to fight off a specific pathogen. Both ways can last for a long time depending on the disease. Though most times, a person will only gain a partial level of protection

However, until now it is still unclear what kind of immunity people who have recovered from COVID-19 have. Furthermore, a vaccine has the possibility to trigger a stronger immune response than natural infection.

If a person has antibodies, are they immune?

For some kinds of diseases such as measles, antibodies may last a lifetime. However, for the coronavirus, no one can tell for sure. It’s still unknown how long covid-19 antibodies last in the blood, or more importantly whether their presence is a sign of immunity. Just because a person has antibodies, it doesn’t mean they are effective at fighting the virus.

“Neutralizing antibodies are ones that halt the virus in its tracks, stopping it from infecting a host cell and replicating. Such antibodies typically recognize the virus’ spike protein, which helps it break into host cells. So far, those kinds of antibodies have been a focus of studies seeking to understand whether a person may be immune.”

“For the majority of people, it does appear that they are generating neutralizing antibodies,” says Aubree Gordon, an epidemiologist at the University of Michigan in Ann Arbor. “So that’s promising.”

“Maybe that means that those memory responses are going to be on the short side,” says Brianne Barker, an immunologist at Drew University in Madison, N.J.

References:

NPR Choice page. (2020, July 23). Npr. https://choice.npr.org/index.html?origin=https://www.npr.org/sections/health-shots/2020/07/23/894670842/how-long-will-immunity-to-the-coronavirus-lastSchimelpfening, N. (2020, October 14). How Long Does Immunity Last After COVID-19? What We Know. Healthline. https://www.healthline.com/health-news/how-long-does-immunity-last-after-covid-19-what-we-know#What-we-currently-know-about-COVID-19-immunityThompson, D. (2020, July 20). How Long Does COVID-19 Immunity Last? The Atlantic. https://www.theatlantic.com/ideas/archive/2020/07/could-covid-19-immunity-really-disappear-months/614377/Thompson, H. (2020, October 16). We still don’t know what COVID-19 immunity means or how long it lasts. Science News. https://www.sciencenews.org/article/coronavirus-herd-immunity-immune-response-antibodies

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