Coronavirus: Single or double dose? What is better for recovered COVID patients?

Recovered patients in India have been advised to wait for at least 3 months post their recovery to get the COVID-19 vaccine jab.

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While the COVID-19 vaccine jab is absolutely essential and offers a lot of beneficial protection even for those who have already caught the virus once, there has been a lot of debate and to and fro around the number of doses a recovered patient may need.

A lot of experts agree that a person who has already contracted COVID-19 once before may only need a single dose of the vaccine, in comparison to someone with no infection history. Even so, there's also contrasting evidence that has suggested that a single dose of the COVID-19 vaccine may not offer much protection against variants, and so to say, increases the risk of breakthrough and reinfection cases.

We are still at the critical juncture of vaccination wherein states are encountering shortages. Globally, too, there has been a lot of discussion around the matter.

Meanwhile, there are also promising hopes of the Johnson and Johnson’s Jannsen single-shot vaccine being brought to India. So, at a time like this, what does a recovered patient really need to know?

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We decode the science behind the single-shot offer and the concerns around the same:

Natural immunity starts to build up post a coronavirus infection and mounts defensive antibodies which remain at their peak for a while. It is believed that the immunity remains at substantial levels for upto 90 days (higher in severe cases), and in some cases, last an entire lifetime which are reasons as to why someone who has recently recovered from COVID-19 needs a delayed dose (or two) of vaccines.

However, while a person who has contracted COVID-19 does gain some level of immunity, there's evidence to suggest that a single vaccine dose, over and above the present level of immunity prompts a good immune response, which could be equitable to the working of two doses, given to someone with zero history or immunity against coronavirus.

While avoidance of a second dose for recovered patients would be able to stretch resources, there are also stronger researches to prove that a second dose may not be actually required. For example, studies have observed that people who have had exposure to SARS-COV-2 mount stronger immune responses with single shots, and tend to react less well with second doses.

It has also been shown that the immunity gained through the first dose, i.e., the antibody levels are often equal, or greater than for the ones who haven't previously been infected and received double doses.

Another scientific study, which has been published in the science journal, Nature, has also found that a single shot was necessary for people who have had COVID-19. The study, which involved 26 participants who had contracted the virus early during the pandemic showed a significantly high immune response with a single dose of mRNA vaccines (Pfizer and Moderna).

A similar study, conducted by a leading hospital chain based out of Hyderabad observed that a single dose of the Covishield (Oxford-Astrazeneca) vaccine not just boosts antibody production, but works well enough to support a recovered patient who takes the vaccine.

One of the reasons why recovered patients may need just a single dose is because of the function played by memory T-cell and B-cell responses. In addition to the presence of natural immunity, vaccine-drive immunity may drive a better and potent antibody response, which is then also better remembered by memory cells. The response of a single dose vaccine was also at par with people who received two doses of the vaccine.

Scientifically and strategically, offering one dose makes sense. At this moment, there's also some level of clinical evidence which supports that previously infected people may require less dosage. However, with the strong evidence, scientists feel that the presumption is complicated. For one, some say that there's still less clarity on the matter, especially since we are facing a surge of cases from mutant variants, such as Delta and Lambda strains, which have become dominant across the world.

There may also be categories of people who may still need assurance of two doses, or booster shots. For example, those who have a known risk of reinfection (older in age, women, have a pre-existing illness or frail immunity), or other risk factors should still prioritize getting full vaccination right now.

The above observations, although helpful, haven't yet been pushed forward as official guidelines, and will require more research. If you are scheduled to get vaccinated, one may still require two full doses to be considered fully vaccinated against COVID-19. Do not delay, skip or avoid your dose, unless you have been specifically advised to do so. The only way the vaccination policies might help right now is by offering a sense of potential security and respite to someone who has recently recovered from COVID-19.