Covid-19 infection survey begins in Portugal

The Covid-19 National Serological Survey began on 25 May and aims to estimate the incidence rate of infection by the new coronavirus in the population residing in Portugal.

This population-based survey, which includes five cross-sectional epidemiological studies, aims to assess the presence of antibodies against the new coronavirus (SARS-CoV-2) responsible for Covid-19 in the population residing in Portugal and to monitor its evolution over time announced the National Institute Ricardo Jorge (INSA).
Speaking to Lusa news agency, the coordinator of the survey, Ana Paula Rodrigues, said that “fieldwork officially starts today [25 May]” across the country and lasts for three weeks.
For its implementation, 1,720 people aged 10 or more and 352 children up to nine years of age will be selected to use one of the approximately 100 laboratories or hospitals of the National Health Service partners to carry out routine laboratory analyses”.
Ana Paula Rodrigues, from the Department of Epidemiology at INSA, said that “a very close monitoring of this work” will be carried out, counting daily how many participants have already been selected to make “some adjustments to the field work” so that it can be completed within the scheduled period.

The survey’s main objective is “to estimate the infection incidence rate in the population residing in Portugal”, she stressed.
“We then intend to have this estimate by age group and by health region in order to be able to compare them with each other, and another objective is to estimate the proportion of infections that will have been asymptomatic or with very slight symptoms, that is, people who have antibodies against the new coronavirus, but have had no symptoms in the previous two months,” she explained.
According to the researcher, the strategy for the selection of participants has already been used in previous serological surveys, such as the one carried out “on vaccine-preventable diseases”, in which people, when they go for routine blood tests at their laboratories, are invited to participate in the study.
“The participation consists of giving a very small amount of blood from the sample already taken initially and to then answer a small health questionnaire to mention whether the person had symptoms suggestive of the disease in the previous two months”, she added.
The results of this first study, which is also the pilot study for this serological survey developed by the departments of Epidemiology and Infectious Diseases at INSA, should be made public during the month of July.
Participating in the survey will have no cost to participants, who will be able to access their results if they so choose, says INSA, who will process all samples.