ABSTRACT
Background People who use drugs (PWUD) have increased risk of acquiring SARS-CoV-2 and having severe courses of COVID-19. However, during the first wave of the pandemic, surprisingly few PWUD tested positive for SARS-CoV-2 in Oslo. Aims: To investigate the seroprevalence of SARS-CoV-2, the antibody responses to virus infections and SARS-CoV-2 vaccines, and the vaccination rate among PWUD compared to the general population. Methods: Design: A prospective cohort study. Setting: Data was collected from residents at six institutions for homeless PWUD and users of a low-threshold clinic for opioid agonist treatment. Data was collected at baseline (N=99) and follow-up (N=25) and consisted of questionnaires and blood samples. Data on vaccination was collected from the National Vaccine Register. Serologic methods included detection of antibodies to different virus proteins, detection of neutralizing antibodies to SARS-CoV-2, and antibodies to Spike-FL, receptor-binding domain of the Spike protein and nucleocapsid from SARS-CoV-2. Results Antibodies to SARS-CoV-2 were detected in 4/99 samples from PWUD in the months before vaccines were available. The corresponding frequency for population-based screening was 2.8%. The levels of serum antibodies to seasonal coronaviruses and EBV in PWUD, were also similar to those measured in population-based screening. The levels of binding and neutralizing antibodies to SARS-CoV-2 measured in samples obtained from PWUD (N=25) after the second vaccine dose were comparable to those observed in healthy controls. Concerning humoral immune responses to COVID-19 vaccination, there was no difference between PWUD and healthy individuals. Eighty-four and eighty-nine per cent had received at least one dose of corona vaccine among PWUD and the general population, respectively. Conclusion Results showed that PWUD did not have increased seroprevalence of SARS-CoV-2 and did not have increased serum antibodies to seasonal coronaviruses and EBV. Vaccine responses were not different from controls demonstrating that vaccination is a viable strategy to confer protection against SARS-CoV-2 in PWUD