The reduction of antibodies six months after being vaccinated against Covid-19 supports the use of a booster dose

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A Spanish study has shown the usefulness of the booster vaccine against Covid.

Specifically, it has concluded that the

The CombiVacs Trial Study Group, led by the Carlos III Health Institute (ISCIII), has analyzed the

up to day 180 (six months) after the last guideline.

The work has been published in

which belongs to

.

Antibody

vaccine , but remain at levels with neutralizing activity, with the complete regimen or with the second dose.

The fact that this protection decreases for

and especially for

and suggests that it would be advisable to assess vaccinations against new escape variants.

The trial started in May 2020 and was designed to evaluate a combined vaccination schedule using a second dose of the Pfizer-BioNtech (Comirnaty) vaccine in people under 60 years of age who had already received a first dose of AstraZeneca (Vaxzevria).

The Spanish researchers have pointed out in the work that the effectiveness may be influenced by the interval between doses.

In other words, a greater antibody response and effectiveness are associated with a longer interval between injections.

In this sense, the authors point out that

in the control group did not have a detrimental effect, but rather

, and that the progressive decrease in protection opens the door to new doses of the vaccine to consolidate the efficacy of the first doses.

On the other hand, they insist on the impact of

given the relevant role of the

responses found in patients with Covid-19 and the cross-reactivity observed in unexposed individuals.

Furthermore, as suggested for the omicron variant, a decrease in virulence could contribute to reduced rates of hospital admissions and death.

It also points to the possible

of an asymptomatic

of the vaccine and causing a "booster-like" response after the first immunization.

Differences according to the Covid variants

The data that has made it possible to analyze humoral immunity - that which is provided by antibodies - and cellular immunity - that which is conferred by T lymphocytes- starts from the

.

All

(study group) and three months (control group) after the first dose.

The researchers

after the second immunization, analyzing antibodies directed at the receptor binding domain (RBD) of SARS-CoV-2, their efficacy against alpha, beta, delta and omicron variants, and the cellular response generated by T lymphocytes measured by the production of Interleukin 2 (IL-2) and interferon- (IFN-).

The results indicate that

, compared to those analyzed one month after the second dose, and that the neutralizing antibodies also decreased their titers.

This decrease is

.

This drop especially affected the

, since only 20% of the patients participating in the trial showed sufficient neutralizing antibody titers to block these variants after those 180 days.

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• covid 19

• Vaccines

• Pfizer Vaccine

• AstraZeneca

• Coronavirus

• Omicron variant

• Delta variant