The United States has just started rolling out the country's two authorized Covid-19 vaccines, but Vox's Brian Resnick writes that some of the more than 20 million Americans who've had Covid-19 are wondering: Do I need to get vaccinated?

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Why people who've had Covid-19 may think they don't need to be vaccinated

According to Resnick, some people who've had Covid-19 may question whether they need to be vaccinated because their bodies have already mounted an immune response against the novel coronavirus and Covid-19—and that immune response could mean they've developed some degree of protection against the virus and the disease. In fact, Resnick writes, scientists in lab studies have found that most people who've contracted the novel coronavirus develop neutralizing antibodies that can render the virus "harmless."

Nevertheless, immunologists and vaccine experts told Resnick that people who've had Covid-19 should get inoculated once vaccines become widely available. Why?

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Why experts say people who've had Covid-19 should get vaccinated

One of the main reasons why experts think everyone should receive a Covid-19 vaccination, including those who've had Covid-19, is because everyone's immune system responds differently to the virus, Resnick writes.

According to experts, documented cases of reinfection from the novel coronavirus suggest some people who've contracted the virus may have had a weak or waning immune response to pathogen, meaning their body hasn't mounted a strong or lasting immunity to the virus. Resnick writes that scientists generally believe when it comes to the novel coronavirus, "the worse the first infection, the stronger the immune response will be."

In an email to Resnick, Akiko Iwasaki, a professor of immunology at Yale University School of Medicine, explained that some people who've had Covid-19 "develop very high levels of neutralizing antibodies and are likely in no need of vaccines, while others develop undetectable levels of neutralizing antibodies" and therefore may need a vaccine to protect against the coronavirus and Covid-19.

Alexander Sette, an immunologist at the La Jolla Institute for Immunology, said he and his colleagues have found that about 90% of people will mount a durable immune response against the novel coronavirus—which can last up to eight months—while about 10% of people will not have as strong of an immune response.

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However, Sette explained that it's not clear which of those categories patients who've been infected with the coronavirus fall into. As such, Sette said that not taking any precautions—including wearing a face mask, practicing social distancing, or getting vaccinated—after an initial coronavirus infection is comparable to "driving a car where you're 90% sure the car has brakes."

That's why experts say people who've been infected with the novel coronavirus still should get vaccinated: to "level out the variability" in immune responses, Resnick writes. Covid-19 vaccines offer patients a more consistent level of protection against the pathogen, experts said.

"During a natural exposure to [the novel coronavirus], there are multiple factors that interfere with a robust immune response," Iwasaki explained. For example, "[t]he exposure dose may be too little." In addition, "The virus interferes with our immune system (both innate and adaptive) to block proper antibody induction," Iwasaki said.

In contrast, Iwasaki said, "vaccines are formulated to provide just the right dose" of the viral protein needed to generate a robust immune response, resulting in a "much more uniform and higher level of antibodies generated with a vaccine."

According to Sette, clinical trial data on the two vaccines currently authorized for use in the United States shows both vaccines have high levels of efficacy, which suggests the inoculations can produce robust immune responses in a majority of people.

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There are some unknowns, however

Still, it's not yet known whether Covid-19 vaccines will boost a person's natural immune response to the novel coronavirus after an initial infection. Experts say, however, that an inoculation against Covid-19 likely won't cause harm to people who've already been infected with the novel coronavirus—and there may be some potential benefits.

In an email to Resnick, Helen Chu, an immunologist and physician at the University of Washington, wrote that although scientists haven't yet determined whether vaccines will offer an immunological boost to people who've had a weak immune response to a natural coronavirus infection, she believes getting the vaccine could be beneficial, because "[a]ntibody wanes over time, and it is likely that the vaccine will boost your pre-existing antibody titers."

Scientists are still working to definitively prove whether Covid-19 vaccines provide an immunological boost to people who've already been infected with the coronavirus, though. According to Resnick, Moderna vaccine scientist Jacqueline Miller recently said the company is "anticipating data in the coming weeks" on whether its Covid-19 vaccine improves the immune response of people who've already been infected.

But in the meantime, experts say that once coronavirus vaccines become widely available, people who've been infected with the novel coronavirus should be vaccinated. "To be safe, I recommend getting the vaccine, even after you recover from [Covid-19], when the vaccines become sufficiently available," Iwasaki said (Resnick, Vox, 12/18).