Introduction:
Available evidence from European countries suggests that migrants are at an increased risk of COVID-19 infection and present higher positivity rates. In Portugal, as in most EU countries, there are no studies on this subject. The aim of this study is to compare COVID-19 infection rates, use of SARS-CoV-2 testing and positivity rate between immigrants, particularly from outside the EU EFTA-UK, and native born in Amadora, Metropolitan Region of Lisbon, Portugal.

Methods:
A longitudinal study was conducted between 1 May 2020 and 31 December 2021 using monthly data from Amadora residents collected from the National Epidemiological Surveillance System (SINAVE). COVID-19 infection rates, number of tests performed per person, and positivity rates were computed for native born, and immigrants (within EU EFTA-UK and outside) adjusting for sex and age using logistic regression.

Results:
We analysed 299 272 tests from individuals living in Amadora. The COVID-19 infection rate was 12 890 per 100 000, positivity rate was 7,4% and the average number of testes per resident was 1,74. Native born COVID-19 infection rate was 13 278 per 100 000 compared with 11 329 per 100 000 regarding immigrants outside EU EFTA-UK. While native born performed 1,6 times more tests, immigrants outside EU EFTA-UK positivity rates were higher (9,8% vs 7.2%). When adjusting for sex and age, immigrants outside EU EFTA-UK had a higher odd of testing positive for SARS-CoV-2 when comparing with native born individuals (OR=1,42 [95% CI 1,36-1,49]).

Conclusions:
Immigrants outside EU EFTA-UK are more likely to test positive for SARS-CoV-2 infection and less likely to perform COVID-19 diagnostic tests. This result suggests an unequal access to COVID-19 testing in Amadora, Portugal. Targeted efforts are needed to improve testing availability for immigrants and to understand reasons underlying these inequalities.