Home-based testing as an approach to estimate influenza vaccine
effectiveness in South Africa, 2022 -- a pilot study
Abstract
Background. Surveillance programmes for influenza and other
respiratory pathogens are important to generate vaccine effectiveness
(VE) estimates and to inform vaccine composition. We aimed to explore
the feasibility and acceptability of home-based testing.
Methods In 3/9 provinces in South Africa, we established a
self-referral system for individuals aged ≥18 years with respiratory
symptoms of ≤10 days duration. Following electronic consent, swab
collection material was delivered to participants who also completed a
questionnaire including self-reported vaccination status. Swabs were
tested by PCR for influenza, respiratory syncytial virus (RSV) and
SARS-CoV-2. A test negative methodology was used to estimate influenza
VE. Results Of 1456 samples collected between 1 December 2021
and 31 August 2022, 73 (5%) tested positive for influenza, 38 (3%)
tested positive for RSV and 394 (27%) for SARS-CoV-2. We subtyped 55%
(40/73) of the influenza positive specimens; 16/40 (40%) were influenza
A (A(H1N1)pdm09; 10/40 (25%)A (H3N2)) and all 14/40(35%) influenza B
were B/Victoria. Only 20% (279/1451) of participants reported
influenza-like illness case definition symptoms of fever and cough.
Influenza vaccine coverage was 11% (157/1454). The overall influenza VE
was 26% (95% confidence interval, -73%;69%). Of the completed
acceptability questionnaires, 123/127 (97%) participants would make use
of the service again. 36% (46/127) of enrolled participants were
recruited through the testing centre’s webpage and 13% (17/127) through
social media. Conclusions Home-based swabbing was feasible and
acceptable. We were able to calculate an influenza VE, although a large
sample size and verification of vaccine status may improve the VE
estimate in the future.