I've recovered from COVID19, why do I need a vaccine?

A recent study in the Lancet (a very prominent journal) found that, among a very young population in Qatar, the efficacy of “natural” infection was 95.7%. This is in line with other studies in Austria, Denmark, Qatar, Switzerland, the UK, and the US, which reported an efficacy of natural infection ranging between 80 and 95%.

So, do “naturally” infected people need a vaccine?

Yes. For four reasons.

First, we’ve known that natural immunity can be highly protective and can last long (see my previous post here). The problem is that the response is random: Some people have protection for a long time, some people have protection for a short time, and some people don’t even get protection. We have no way to predict who will land in each category yet (Harvard is working on it). The risk of reinfection after natural infection is 2 -5 times higher with Delta than with vaccines. Vaccines induce a pretty uniform and clean response (unless you’re immunocompromised).

Second, getting a vaccine, even for people who have already recovered from COVID-19, strengthens your immune response (antibody and T-cell protection). This is because you get more “doses” of virus protection (one more dose from J&J and two more doses from Moderna/Pfizer). For the mRNA vaccines, this second dose is key for longevity.

Now, if you recover from COVID19 and get the first mRNA vaccine dose, do you need the second dose? This is highly debated among scientists. This strategy seems to work, but we’re waiting for more evidence to change policy.

Third, the vaccine looks to better protect against variants than natural infection. This Qatar study was before rampant spread of variants of concern (as well as other factors, like younger crowd, different level of public health compliance, etc). We have reason to believe natural infection just doesn’t work as well against new variants.

For example, up until now, Israel has restricted previously infected individuals from getting the vaccine because they were considered protected. Israel has been incredibly methodical in COVID-19 testing throughout the entire pandemic. So, the Israelis have a good handle on who was infected with the virus.

But this policy initiated an intense debate among scientists once variants of concern started spreading. This eventually sparked a small study (and others), in which scientists took blood samples among healthcare workers at three time points:

  1. After “natural” infection (participants were considered mild or asymptomatic);

  2. Before vaccination;

  3. After vaccination.

Then, scientists “infected” the blood samples with variants of concern to see how well antibodies responded. What did they find?

  • Panel A and B: Vaccines were better at increasing the number of neutralizing antibodies than natural infection. In other words, you have more soldiers.

  • Panel C and D: Vaccines had more neutralizing antibodies against B.1.351 (variant in South Africa) and P.1. (variant first detected in Brazil) compared to natural immunity. This also probably means vaccines can protect against the NY variant and new “double” variant first discovered in India.

So, Israel changed directions and vaccines are now open (and encouraged) for everyone.

Another study (among 20 adults) found that both natural infection and vaccine infection produces enough neutralizing antibodies for B.1.1.7. Interestingly, they also found that the number of neutralizing antibodies is higher among vaccinated compared to infected patients. This may mean that the vaccine response will last longer among vaccinated (compared to naturally infected).

Fourth, the immune system is messier from natural infection. Natural infection may work, but to a lesser effect because its all over the place; its not as focused as vaccine immunity. Natural response hits a lot more targets and not all of them may be beneficial.

Natural immunity is not a viable public health solution.

If we let this virus rage in the name of “natural protection”, we will loose about 300,000 more American souls to a preventable disease. We’ve already lost 627,000. And that’s “just” mortality. That doesn’t take into account hospital costs, long COVID19, and quality of life. Natural infection comes with lots of risk while vaccines come with very, very little.

As a recent Atlantic article nicely articulated: “Your grandparents, elderly neighbors, and immunocompromised friends will be safer if you’re vaccinated, even if you’ve already been infected. Vaccines aren’t just about building a defensive wall around safe young bodies. We’re also collectively building a wall around the more vulnerable members of society. And little holes in the wall can lead to unnecessary deaths.”

Bottom line: Natural immunity is okay against old variants. No vaccine is perfect, but the vaccine seems to work better, especially among variants of concern.

Love, YLE

I would like to thank two amazing scientists that answered way too many questions from me way too early this morning. Dr. Miguel Sildana, a virologist, and Dr. Michelle Kinder, an immunologist.