The World Health Organization (WHO) has recommended that a second Covid-19 booster dose be given to those groups that are most vulnerable to severe illness due to reduced immunity against the Omicron variant.

These groups include the elderly, people with immunosuppression and all adults with chronic diseases, as well as pregnant women and healthcare workers. If this time frame is exceeded, the new booster should be given as soon as possible.

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

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

In Portugal, the process of administering the second booster dose (fourth dose) started on 16 May, 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 400,000 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 by SARS-CoV-2, which causes Covid-19, a 24 percent reduction from the previous week, especially in Africa and Europe, where the reduction was almost 40 percent.

The number of deaths worldwide fell by an average of 6 percent, despite an increase in some areas of Asia.