Abstract:
OBJECTIVES : Influenza vaccine effectiveness (VE) and coverage data
for sub-Saharan Africa are scarce. Using a test-negative case–control
design, we estimated influenza VE annually among individuals with
influenza-like illness presenting to an outpatient sentinel
surveillance programme in South Africa from 2010 to 2013. A
knowledge, attitudes and practices (KAP) influenza vaccine survey
of programme clinicians was conducted in 2013.
SAMPLE : In total, 9420 patients were enrolled in surveillance of
whom 5344 (56.7%) were included in the VE analysis: 2678 (50.1%)
were classified as controls (influenza test-negative) and 2666
(49.9%) as cases (influenza test-positive).
RESULTS : Mean annual influenza vaccine coverage among controls
was 4.5% for the four years. Annual VE estimates adjusted for age,
underlying medical conditions and seasonality for 2010-2013 were 54.2% (95% confidence interval (CI): 2.4–78.6%), 57.1% (95% CI:
15.5–78.2%), 38.4% (95% CI: 71.7–78.1%) and 87.2% (95% CI:
67.2–95.0%), respectively. The KAP survey showed that >90% of
clinicians were familiar with the indications for and the benefits of
influenza vaccination. CONCLUSIONS : Our study showed that the vaccine was significantly protective in 2010, 2011 and 2013, but not in 2012 when the circulating A(H3N2) strain showed genetic drift. Vaccine coverage was low despite good clinician knowledge of vaccination indications. Further studies are needed to investigate the reason for the low uptake of influenza vaccine.
