The World Health Organization (WHO) recommended yesterday, Thursday, the administration of a second booster dose of the covid-19 vaccine for the groups most vulnerable to severe disease, due to reduced immunity against the Omicron variant.

These groups include the elderly, from which age it is up to each country to define, people with immunosuppression and all adults with chronic diseases, as well as pregnant women and healthcare professionals.

At a press conference with the strategic advisory group of immunization experts cited by Lusa, it was explained that the optimal interval between the first and second booster doses is four to six months, the same period after which it was concluded that the effectiveness of covid-19 vaccines begins to decline.

If this time frame is exceeded, the new booster should be administered as soon as possible.

According to the expert group's evaluation of the effectiveness of Pfizer's and Moderna's vaccines, children and young people are among the lowest priority groups because they are less vulnerable to serious illness.

Joachim Hombach of the WHO and the advisory group also said that it is still uncertain whether or not experts will recommend booster vaccination for the general population or a vaccine combination specific to the Omicron variant.

In Portugal, the process of administering the second (fourth) booster dose began on May 16, covering people aged 80 or older and all residents of Residential Structures for the Elderly (ERPI).

The administration of this second booster dose is part of the strategy to improve protection for the most vulnerable population and, according to the Directorate General of Health (DGS), by the end of July more than 400 thousand people had already been vaccinated with this new dose.

In the same press conference, the WHO also indicated that last week there were about 5.4 million new cases of infection with SARS-CoV-2, which causes covid-19, a reduction of 24% compared to the previous week, with a focus on Africa and Europe, where the reduction was almost 40%.

The number of deaths worldwide fell by an average of 6%, although there was an increase in some parts of Asia.