COVID-19: Nationwide study to evaluate number of infected Poles

A nationwide study will be conducted in Poland to evaluate the exact number of people who have been infected with coronavirus and those who have acquired immunity to the COVID-19 disease.

Commissioned by the health minister, it will be carried out by the Medical Research Agency (ABM) and the National Institute of Public Health (PZH).

According to scientists, around 20-30 percent of coronavirus infections are asymptomatic. Due to this, it is difficult to evaluate the incidence rate of COVID-19 diseases and infections on the basis of the registered cases. Official data does not reflect the true state of the spread of the virus.

The ABM in cooperation with the PZH based in Warsaw are launching a "nationwide COVID-19 sero-epidemiological study: OBSER-CO," in order to evaluate the real spread of the SARS-CoV-2 virus in Poland," ABM wrote in a statement sent to the Polish Press Agency (PAP).

Sero-epidemiological blood tests identifying people who have antibodies against SARS-CoV-2 are planned as part of the project.

The comparison of the percentage of people, in whom antibodies have been found, with the percentage of registered cases in relation to the population (cumulative incidence) will make it possible to define the number of unrecognised cases. In the majority of countries, where such a study has been carried out, the estimated percentage of unrecognised cases varies from 95 to nearly 99 percent.

The evaluation of the percentage of unrecognised SARS-CoV-2 cases will help epidemiologists to prepare a better model of the epidemic course. A large proportion of people, who are immune to the virus, slows down its spread and makes it possible to better control the epidemic. As a result, it also makes it possible to take significant organisational decisions and ease restrictions. Without this information, decisions regarding possible restrictions must be made on the basis of more pessimistic forecasts.

The OBSER-CO study is to be carried out in three stages. During the first two (March and July 2021), in all, 11,850 people from each of Poland's provinces and from all age groups will be tested. The third stage, to take place in December 2021 and January 2022, will cover 6,300 people over the age of 60.

There will also be a questionnaire for tested people regarding their work, contacts with infected people, or participation in public events, among other questions. The data obtained during the study are planned to answer questions regarding immunity and the most common sources of exposure to the virus.

"The obtained results evaluated in relation to the territory they come from as well as to age and occupational groups are expected to offer additional information and may help modify previously identified priority groups in the population eligible for vaccination," reads the statement.