Data collection and management
At enrolment, participants completed a questionnaire that included
questions about demographics, comorbidities, previous SARS-CoV-2
infection and SARS-CoV-2 vaccination history. Study staff then contacted
participants weekly, using a standard questionnaire, to ask participants
if they had experienced any symptoms in the past week (fever, cough,
general weakness, fatigue, headache, muscle ache, sore throat, runny
nose, shortness of breath, lack of appetite, nausea, vomiting,
diarrhoea, altered mental status, loss of taste, or loss of smell), and
to ask about the details of any new COVID-19 vaccines participants had
received.
We advised all participants who became symptomatic to attend testing
facilities at the study hospitals, where trained nurses collected
nasopharyngeal swabs, which were tested at on-site government-accredited
laboratories or other Ministry of Health laboratories for SARS-CoV-2 by
RT-PCR. Symptomatic participants
completed an additional survey that included information about date of
symptom onset, clinical care-seeking, and details of PCR testing and
results. PCR-positive participants were interviewed again 30 days after
their positive test, at which time further details about their course of
illness, medical care, hospitalization, and complications were
collected.
Data from interviewer-led questionnaires and laboratory records were
entered and stored securely using the Sorgular.az platform (Azerbaijan
Public Health Reform Center). Participants’ reports of positive PCR
results were verified using the two national SARS-CoV-2 laboratory
databases – the Etabib electronic medical records database, and the
Ministry of Health (MoH)/Mandatory Health Insurance database – to
which all SARS-CoV-2 PCR tests performed in public and private
laboratories in the country are required to be reported. Participants’
COVID-19 vaccination history was verified using the national vaccine
registry (Rendezvous, Azerbaijan Ministry of Health). Study staff
contacted participants to resolve discrepancies between data from
questionnaires and those from national databases, and to complete
questions from study questionnaires that had not been answered.