Incidence of Adverse Events Among Healthcare Workers Following H1N1 Mass Immunization in Ghana

Abstract

Cases of the A(H1N1) 2009 influenza were first recorded in Ghana in July 2009. In June 2010 when prioritized vaccination against the novel A(H1N1) 2009 influenza virus started in the country, health workers were among the selected groups to receive the vaccination. The aim of this study was to determine the distribution and types of adverse events reported following immunization of healthcare workers at the Korle-Bu Teaching Hospital from the day vaccination started until 1week after the end of vaccination. Safety data collected during the A(H1N1) 2009 influenza vaccination of health workers at the Korle-Bu Teaching Hospital (Accra, Ghana) were used for this study. All workers aged 18years and over were eligible for vaccination. For uniformity, 0.5mL of Pandemrix(®) (equivalent to 3.75μg of hemagglutinin antigen) was administered intramuscularly into the deltoid muscle of the left arm. Each vaccinee was issued with a card and was advised to report any adverse events following immunization (AEFI) to designated health workers for follow-up. Incidence rates of adverse events were estimated and compared with the Pandemrix(®) Summary of Product Characteristics (SPC) RESULTS: A total of 5870 people (64.9% females) with a mean age of 34.0years were vaccinated. In total, 140 vaccinees reported adverse events. The mean age among vaccinees reporting adverse events was 36.1years. The overall incidence of vaccinees reporting adverse events and the overall incidence of adverse events was 232 (95% CI 199-320) per 10,000 people and 930 (95% CI 820-1070) per 10,000 people, respectively. In particular, we found no difference in the way males reported AEFI compared with females (Chi-squared [χ(2)]=0.59; p>0.2), and we did not find any association between age as a categorical variable and vaccine adverse event reporting (χ(2)=5.24; p>0.1). There were only three serious cases that led to hospitalization. All three cases occurred within 24 hours of receiving the vaccine. The incidence rates for the various reported events were all lower compared with those in the Pandemrix(®) SPC, but while injection-site pain was the most frequent in the SPC and other foreign studies, we recorded headache as the most frequent. Even fatigue, muscle/joint aches and fever had higher incidence rates compared with injection-site pain. Tachycardia (n=6), tinnitus (n=1) and decreased appetite (n=4) were reported although were not included in the SPC. The most prominent adverse events reported were headaches, dizziness, muscle and joint aches, weakness, fever and injection-site pain. Although similar events were reported in other studies, the incidence was different and there were a few differences in the most frequently reported events. More studies of a similar nature should be encouraged in low- and medium-income countries to bridge the information gap with the developed world.