The booster dose prevented almost 450,000 infections in the sixth wave of covid in Spain

Vaccines saved Spain from what could have been disastrous consequences of the sixth wave of covid.

It was known that thanks to his protection, hospitalizations and deaths were drastically reduced, despite registering many more infections than before immunization.

Now, a study by the Carlos III Health Institute, published this Friday in the journal

, shows that the vaccine also stopped transmission: people who had received a booster dose were 51% less likely to become infected than those who only completed the first course.

According to this calculation, 1,860 infections were avoided for every 100,000 people who had received it, which represents almost 450,000 infections, the majority among the most vulnerable population, which is the one that received the most booster dose coverage.

The study has analyzed data from more than four million people over 40 years of age between January 1 and February 6, 2022. People with complete primary vaccination were followed up, and the risk of infection was compared among those who received a booster dose and those who did not receive it, thanks to the vaccination and infection records of the National Health System.

As stated in an editorial published by

publishes accompanying the article, despite the fact that the study has some weaknesses such as some confounding factors and that many infections during that wave were not reported, "it is important" because it collects a large population sample during the most contagious wave of covid in Spain, driven for the omicron variant.

The study comes to ratify part of the knowledge that was already known, and adds new nuances.

Other research had shown how, as the injection time passes and the virus mutates, the vaccine loses effectiveness: although it maintains very good levels of protection against serious illness and death, it is less and less useful in preventing infections.

This new publication shows how the booster dose, without having the same levels that the vaccines showed in the trials (in a controlled population and without virus mutations), continue to protect up to a month after administration (the study analyzes up to 34 days after ).

The more time that passes between the primary vaccination and the booster, the better the effectiveness.

Marcos López Hoyos, president of the Spanish Society of Immunology, believes that a study in such a large population provides very good insight into how vaccines work.

He “he confirms that the production of antibodies shoots up in the first few months, for some people more than for others, and then declines.

And we know that protection from severe disease lasts longer,” he notes.

Despite this protection, López Hoyos does not believe that the results support new vaccinations as a strategy to prevent contagion with the formulations that are now on the market: “That is why we have masks.

50% is not enough and each wave would have to be vaccinated, which makes no sense”.

The doctor considers that in order to administer new doses to the population that already has the booster, it will be necessary to wait until there are vaccines designed for the new variants or that are pancoronavirus.

Pedro Gullón, from the Spanish Society of Epidemiology, considers that the results of the study are as expected: “51% protection is expected, it is lower than that with old variants, it makes sense.

But he gives us a vision: sometimes we can think that the new variants are new viruses, and no, they are the same, even though there may be more immune difficulties ”.