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How long does it take before you get coronavirus immunity from a vaccine?

Published Dec 31st, 2020 1:47PM EST
Coronavirus Vaccine

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  • Three coronavirus vaccines have received emergency authorizations so far in different markets, and two of them are already available in the US.
  • Coronavirus immunity isn’t immediate, which is key information that people should have.
  • It takes between a few days to a few weeks for the body to develop the types of cells that will fight off a COVID-19 infection.
  • People who are vaccinated are advised to continue observing health measures like wearing masks, social distancing, and frequent hand washing.

The first three coronavirus vaccines that received emergency use authorization after clearing Phase 3 clinical trials are already in use around the world. The Pfizer/BioNTech drug is available in the UK, US, and European Union. Moderna’s drug is being used in the US, with other markets to follow. The AstraZeneca/Oxford vaccine was authorized in Great Britain this week, and vaccinations will start on Monday. The initial supply is limited, as pharmaceutical companies are ramping up production. Hundreds of millions of doses will be available next year so that anyone looking for a vaccine can get one — currently, only at-risk people can be immunized.

Now that vaccination campaigns have started, everyone interested in vaccines needs to understand how protection against COVID-19 is acquired and how long it takes for immunity to develop. That’s because protection isn’t immediate, and people who get vaccinated still risk catching and spreading COVID-19. Incidentally, that’s the reason why face masks, social distancing, and frequent hand washing are still advised even after vaccination.

The world has at least one other vaccine available to the general public, and that’s the Russian jab that was authorized back in August even before the Phase 3 trial started. In mid-November, just as Pfizer was releasing its coronavirus vaccine data, a report from Russia indicated three Russian doctors were infected with the virus after being vaccinated. Local authorities who confirmed the news fumbled the initial explanation, which further raised suspicions about Russia’s transparency on vaccine research. Officials initially said that the doctors contracted the illness before taking the first shot. Later, they said the doctors might have been infected after receiving one or two doses of the vaccine. The Russian health ministry then said that a person is immune three weeks after the second vaccination, so COVID-19 protection wouldn’t develop until about six weeks after the first jab.

Fast-forward to late December, and you’ll find reports saying that an ER nurse who received the first Pfizer shot tested positive six days later. People on the fence about the COVID-19 vaccine might see that as proof the vaccine is useless. In reality, that couldn’t be further from the truth.

It takes time for the immune system to develop the components that can recognize the coronavirus and eliminate it. “We know from the vaccine clinical trials that it’s going to take about 10 to 14 days for you to start to develop protection from the vaccine,” Dr. Christian Ramers told ABC News.

“That first dose we think gives you somewhere around 50%, and you need that second dose to get up to 95%,” he added. The doctor, an infectious disease specialist at Family Health Centers of San Diego, said that what happened to the nurse is not unexpected at all. “If you work through the numbers, this is exactly what we’d expect to happen if someone was exposed.” The fact that SARS-CoV-2 can incubate for up to two weeks before the onset of symptoms could also explain why a vaccinated person might still get COVID-19. Contracting the virus before the first vaccine shot is likely to result in a case of COVID-19, as the vaccine would not have had time to induce the desired immune response.

The CDC has an information page that explains exactly how coronavirus immunity is formed, whether it’s a response to an actual infection or from a vaccine. “The first time a person is infected with the virus that causes COVID-19, it can take several days or weeks for their body to make and use all the germ-fighting tools needed to get over the infection. After the infection, the person’s immune system remembers what it learned about how to protect the body against that disease,” the agency wrote. The CDC also describes the types of cells that are created during an infection or following a vaccine:

  • Macrophages are white blood cells that swallow up and digest germs and dead or dying cells. The macrophages leave behind parts of the invading germs called antigens. The body identifies antigens as dangerous and stimulates antibodies to attack them.
  • B-lymphocytes are defensive white blood cells. They produce antibodies that attack the pieces of the virus left behind by the macrophages.
  • T-lymphocytes are another type of defensive white blood cell. They attack cells in the body that have already been infected.

The B and T cells appeared in various immunity studies recently, with one paper saying coronavirus survivors develop strong B and T cells. The lymphocytes were still present in bloodstreams some 8 months after the initial infection. The CDC doesn’t offer a timeframe for COVID-19 immunity but says it takes a few weeks for the body to produce the necessary white blood cells.

It typically takes a few weeks for the body to produce T-lymphocytes and B-lymphocytes after vaccination. Therefore, it is possible that a person could be infected with the virus that causes COVID-19 just before or just after vaccination and then get sick because the vaccine did not have enough time to provide protection.

The CDC also makes it clear that most vaccines will require a second shot a few weeks after the first, and that precautions are still necessary, like masks and social distancing.

A recent development in the UK also indicates that health officials have faith in the immune response that a single vaccine dose can generate. The UK announced a massive change in vaccination protocol, at least for the Oxford drug. The local regulator said that the second dose could be administered anywhere between 4 to 12 weeks after the first, rather than after 28 days. The government’s goal is to protect as many people as quickly as possible.

Finally, there’s one other key aspect to consider when looking at COVID-19 vaccines: the drugs won’t necessarily prevent infection. Vaccinated people might still catch the virus even after the immunity is formed, but they will not develop severe versions of the illness. As more time passes, doctors will also be able to explain another mystery related to vaccines. Are vaccinated people who still catch COVID-19 able to spread the disease? Immunized individuals can get infected, and the virus can infiltrate cells in the nose. The vaccine will prevent the virus from harming the lungs, but people might still be able to infect others. Scientists don’t yet have definitive proof that vaccinated people are incapable of spreading the virus.

Chris Smith Senior Writer

Chris Smith has been covering consumer electronics ever since the iPhone revolutionized the industry in 2008. When he’s not writing about the most recent tech news for BGR, he brings his entertainment expertise to Marvel’s Cinematic Universe and other blockbuster franchises.

Outside of work, you’ll catch him streaming almost every new movie and TV show release as soon as it's available.