What Scientific Evidence Supports The Third Dose Of Vaccines Against Covid-19

Israel, the United States, and some European countries, including Spain , have moved towards the administration of the third dose in, first, the patients at higher risk and, perhaps, the rest of the population later. However, it is a decision that has not yet found certain support in the scientific community or the World Health Organization (WHO).

To shed some light on the reasons for a reinforcement puncture, Marcos López Hoyos, president of the Spanish Immunology Society (SEI) and former secretary of the Spanish Transplant Society (SET), has published an article in the Agency Sinc where he concludes that “there is still no published data to support the need for a third dose for all.” However, he does point out that some studies “suggest that they could benefit people with transplants.”

The main reason for the third dose is that, in theory, antibodies are lost over time. However, Marcos López Hoyos points out that “the data has not yet been published in any scientific journal.” What is known to date, continues the expert at the Sinc Agency , is the duration of circulating antibodies in the blood published by Pfizer / BioNTech -up to 90 days-; of Moderna -something more than 200 days-; and Janssen – antibodies and specific CD4 T cells against protein S last for eight months.

“Curiously, the importance of only antibodies is adduced, but data on the persistence of memory B and T cells are not shown or discussed? Janssen does have them?”, Explains the expert. “These are precisely the populations that, together with long-lived plasma cells, are intended to be induced with vaccination so that our immune system responds quickly and specialized in the event of a new encounter with the virus,” he adds.

Some Scientific Evidence for Immunosuppressed People
The president of the Spanish Immunology Society points out, however, that there may be a situation in which the third dose is more scientifically justified for the moment. This is the immunocompromised population, such as transplanted people.

True, it has been shown that in solid organ transplants the antibody response with messenger RNA vaccines falls to 30-40%, while in the general population it is 90%. A deficiency that could be reversed with the reinforcement injection, since several single-center studies have shown that the third dose is capable of inducing antibody production in 30-50% of seronegative patients after the second dose.