Yes…and no. A past COVID-19 infection does provide good protection against re-infection and severe disease–IF you survived your first infection. Vaccination is still by far the safest way to get your first look at the SARS-CoV-2 spike protein and build immune defenses for a future encounter.
A recent meta-analysis of 65 studies from 19 countries looked at how well a previous SARS-CoV-2 infection protected against re-infection with the virus. The study found that a previous infection protected well against re-infection with the original, Alpha, Beta and Delta variants (82% protection). But a previous infection was much less protective against infection with the Omicron variant (45% protection).
The good news is that protection against severe disease (hospitalization and death) from a re-infection remained high, even for the Omicron variant.
Overall, the authors conclude that protection from a prior infection is at least as good as two doses of the mRNA vaccines, but “must be weighed against the risks of severe morbidity and mortality associated with the initial infection.”
What do we make of this evidence?
Like many things COVID-19, the concept of “natural immunity” became a polarized talking point during the pandemic. From your immune system’s point of view, both the vaccine and the nasty virus are both “natural.” When this study came out, some pundits were quick with “I told you so” stories implying that getting infected is somehow as good (or better) than getting the vaccine.
We recognize this type of rhetoric gets confusing, so we’re here to clear it up:
Getting infected with SARS-CoV-2 in order to AVOID GETTING INFECTED with SARS-CoV-2 makes no sense. By definition, this study only included people who survived their original infection. Those who died were not around to be at risk of re-infection.
Image credit: xkcd comics
But as we know, infection (and 
) happens. If you survive, a previous infection DOES provide good protection against re-infection and importantly, severe disease. This is really good news given that such a large percentage of the population has now been infected, especially during the Omicron waves. As with vaccine-induced immunity, protection against infection drops a lot with a new variant that is different from your original infection/vaccine, but protection from severe disease is more durable.
“Hybrid immunity”-a combination of vaccine and infection induced immunity- provides greater protection against re-infection than either source alone. A recent study found the effectiveness of hybrid immunity against hospital admission or severe disease with the Omicron variant was 97% at 12 months compared with 75% after infection alone.
Again, this is good news given how many people now have both a COVID-19 vaccination series and at least one infection under their belt. This hybrid immunity is likely what’s making the peaks of our new COVID waves shallower over time. But this means for people who ONLY have infection and no vaccine-induced immunity, you still have room to boost your protection.
This study did not examine Long Covid as an outcome. There is suggestive evidence that vaccination, both before and after an infection, can reduce the risk of Long Covid.
While it’s not true that getting infected is preferable to vaccination, this research can inform policy discussions about vaccine mandates and passports. These data suggest that evidence of prior infection could be counted as proof of immunity, as some countries did when requiring proof of vaccination for entry.
BOTTOM LINE:
Previous infections are protective against re-infection and severe disease. Good news!
Don’t get infected on purpose. Over a million dead Americans didn’t get to benefit from their “natural” immunity. Many millions more suffered greatly in the hospital and ICU and with Long Covid to get theirs.
Vaccines are the safest way to get your protection and provide a boost even if you’ve already been infected. Both infection and vaccine immunity wane over time- so stay up to date on your shots.
Stay Safe, Stay Well.
Love,
Those Nerdy Girls
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