If You’ve Had Covid, Do You Need the Vaccine?

If You’ve Had Covid, Do You Need the Vaccine?

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So-called natural immunity varies from patient to patient, scientists say. Immunization is still the best choice after recovering from the disease.

By Apoorva Mandavilli for The New York Times|

As vaccine mandates roll out, a national debate has been brewing about whether the rules should apply to those who have so-called natural immunity from a previous coronavirus infection.

Politicians, athletes, law professors and psychiatrists have all weighed in on the dispute, which revolves around the central question: Do people who have had Covid really need the vaccine?

Apoorva Mandivilli recently set out to answer the question, and found that — like nearly everything about the virus — it’s very complicated.

The bottom line: People who have recovered from a Covid infection have some protection against the virus. But the strength and durability of their immunity depends on their age, health status and the severity of the initial infection. A vaccine would amplify their immunity, granting long-lasting protection against all the variants.

“Unlike vaccines, which seem to produce a pretty strong immune response in almost everybody, natural infection is a bit more variable,” Apoorva told me. “How strong and how durable your immunity is seems to depend on how severe the infection was — the more severe, the more protective.”

There are some benefits, however, to natural immunity. Antibodies from prior infection are more diverse and are able to fend off a wider range of variants than those produced by vaccines. Natural infection also stimulates defenses in the nose and throat — exactly where they are needed to prevent a second infection — while the vaccines produce antibodies mainly in the blood. Fragments of the virus may also persist in the body for weeks after infection, which gives the immune system more time to learn to fight it, while the proteins carried by the vaccine quickly exit the body.

“But long term, it’s not bulletproof against infection, just like vaccines,” Apoorva said. Natural immunity seems to offer protection for at least a few months, or possibly a year, against re-infection that produces symptoms.

Another big unknown is how well natural immunity protects against the newer variants. Most studies tracking natural immunity were competed before the rise of the Delta variant, and more recent research is patchy.

“Many months ago, before Delta, there would have been an argument for people who have had Covid to say that they don’t want to get vaccinated,” Apoorva said. “But now we know that not everybody produces a really strong response to being infected. They seem to not do quite as well against variants as they did against the original virus.”

“We also know that they can get reinfected after a certain point, even if they don’t get very sick, and they can spread the virus to others if they get infected,” she added. “So for all those reasons, it still makes sense, and it’s still important for people to get vaccinated. Both for their own ongoing health, but also to protect others.”