Coronavirus vaccination: Do recovered COVID-19 patients also need a booster shot?

With all the benefits that COVID-19 vaccination does grant, booster shots have been much talked about right now. A lot of countries have started to press for booster vaccination, considering the virulent strains which are in circulation and the lowering efficacy against milder forms of illness.

Even though there may be a long wait till booster shots become a reality in India, the benefits have been observed to be much promising, especially for those who may not be capable of producing an efficient immune response in the first place. But what does it mean for someone who has had prior infection, and has received both vaccine shots as well?

Now, while we have a lot of emerging studies that have specified the benefits recovered COVID-19 people can have from a single dose of COVID-19 shot, being immunocompromised could possibly dim down the vaccine's efficacy over time. At the same time, there's also some research that has found that natural immunity could be stronger and promising than vaccine-driven immunity. So, in such a scenario, would booster shots be also needed by someone who already has some level of natural immunity?

Booster shots or additional COVID-19 doses have been widely studied for the effect they have had on extending the immune protection guaranteed by existing COVID-19 vaccines. While the experimental COVID-19 vaccines can be prone to diminishing immunity after a foreseeable while (9-12 weeks) with the rising variants, delivering additional shots can prep the immune system into mounting a stronger, more effective immune response and spike up antibody counts as well, which, with certain vaccines can not tackle lowering variant-driven protection, but also provide more longer-lasting immunity.

The most effective response, as per recent clinical studies have been seen with mRNA vaccines (Pfizer and Moderna), Johnson and Johnson's single-shot vaccine and the Oxford-Astrazeneca vaccine.

Even though the requirement for booster COVID shots come at a time when there's a crunch for vaccine resources, the jabs, according to specialists benefit the ones who may have preconditions that affect their immune system from doing its job well or may not be equipped enough to produce protective antibodies in the first place. This can include the ones who are immunosuppressed or fighting chronic conditions, which may interfere with vaccine protective powers.

The shots, according to some experts may also be strongly needed by those who have been previously fully vaccinated, have a higher exposure limit, i.e. are more susceptible to waning immunity. As we go further, shots may not only become an annual affair, but also be prioritized for those of age, or more established risks. While more research is needed to confirm the same, this may also include the ones who have been previously infected, and may also be at the risk of chronic illness or conditions.

There's also a growing debate between experts and recovered people as to which form of immunity, against COVID-19, may be more dependable and protective right now.

However, while both are similar in many aspects, the answer is a little complicated.

Natural immunity occurs when the body fights the infection (unvaccinated) builds antibodies by its own self. In contrast to this, vaccine-driven immunity spikes ample antibodies in the system by the introduction of an artificial (or a harmless piece of spike protein) agent, which mimics infection and builds immunity. For this reason, it is also known as artificial immunity.

While both tend to build a protective immune response to the virus, vaccine-driven immunity has been clinically studied to offer a lower chance of severity, mortality risk against COVID-19. However, natural immunity could be longer-lasting, but not uniform. Natural immunity can greatly differ for someone who has had a mild or severe infection, for example.

Even though there are many prospective advantages of getting a COVID vaccine shot when you have been previously infected, there are certain studies that do highlight that natural immunity could be more long-lasting and in fact, more powerful than vaccine-driven immunity.

One such recent study, done by Israeli researchers have found out that a prior history of COVID-19 infection mounts a higher, more effective immune response against the Delta variant, in comparison to two doses of the Pfizer COVID vaccine, which is an mRNA vaccine touted to have high efficacy.

The study also made another surprising observation. Vaccinated people, with no history of COVID-19, had a higher likelihood, as much as 6-13 times to get infected with Delta variant than unvaccinated people who'd had COVID-19 before, the researchers found.

The findings, inferred from the one-of-a-kind real-time study make a case highlighting that a past infection, i.e. having had COVID-19 before offers stronger odds of protection for the body, than vaccination alone, could. This, according to some experts, happens because of the way the body remembers the infection and mounts a stronger response with a vaccine (or reinfection).

With all the benefits, it's important to remember that there's little evidence that does support the backing of booster shots, for the generalized population. From the side-effects to the actual need, there are some who say that the shots may be needed on a case-to-case basis.

There’s also some research that has seemingly concluded of the protection recovered people stand to get from a single shot of the vaccine, which could be as helpful as lifetime protection. More particularly, recovered people, who do get mRNA vaccines have the highest odds of protection right now and thus, further research is needed to ascertain whether or not recovered people, too, may be prioritized for additional shots.

Another study also highlighted that people who have had COVID-19 may continue to develop antibodies for upwards of a year's time, providing them ample protection right now.

However, a lot of this also depends on individual factors and illness risk. For example, someone with chronic immunity lowering conditions, or with high infection risk (such as older people, those with two or more comorbidities) may be in need of strengthened protection, which only a booster shot may be able to provide.