The study, conducted by the Gulbenkian Science Institute (IGC), involved 260 elderly people from five homes, in addition to 160 employees, in which almost all (98.1 percent) continued, at the end of the same period, with antibodies against SARS- CoV-2. In a statement, the IGC said that the data "confirms that, similarly to what happens with other vaccines, the decrease in antibodies generated by vaccination" against Covid-19, a respiratory disease, "is faster in the elderly population".

The IGC emphasizes that "the trend of depletion of antibodies began to be noticed three months after the second dose in about 15 percent of the participants" aged over 70 years. Both seniors and employees of the five homes received the Pfizer/BioNTech vaccine, administered in two doses spaced apart. For the IGC researcher Carlos Penha-Gonçalves, coordinator of the study, cited in the statement, "the decrease in the levels of vaccine antibodies over time is natural and expected and does not mean that there is no protection against the infection". According to the IGC, "People who had an antibody response soon after vaccination are expected to have developed an immunological memory that will allow them to fight the infection in subsequent contacts with the virus: that is the principle of vaccination."

However, "while the virus is circulating in the population, as it is the case, it is essential that individual protective care is maintained", such as the use of a mask, physical distance or hand hygiene, "even after the process of vaccination and over time". The study evaluated the persistence of antibodies induced by vaccination against covid-19 and followed by another that measured the effectiveness of the vaccine in the production of antibodies also in residents and employees of nursing homes. In the elderly, the production of antibodies is slower and its fall is faster than in younger people.

According to the Gulbenkian Science Institute, it will be "important to continue to monitor the evolution of the drop in antibodies over time", particularly in the elderly, population more vulnerable to covid-19 due to their age and the weakness of their immune system . "The conduct of screening is an essential tool to ensure the monitoring of the evolution of the vaccine response and obtain data to support decisions on possible revaccination and vaccines to be used", stresses the IGC, which has carried out studies on the effectiveness of different vaccines against covid-19 in different ages and professional groups.