Adverse events following immunization among the elderly having booster COVID-19 vaccine: an active surveillance in Guiyang city

  Objective  To examine the incidence of adverse events following immunization (AEFI) among old people receiving booster dose of coronavirus disease 2019 (COVID-19) vaccine and to provide reference data for evaluating the safety of COVID-19 vaccine booster immunization in the population.

  Methods  Using a self-designed questionnaire on AEFI, we conducted person-to-person telephone interviews among 1 157 vaccinees aged 60 years and above 7 – 14 days after receiving booster dose of COVID-19 vaccine at a community healthcare service station between October 2021 and March 2022.

  Results  Of all the elderly interviewed, 122 (10.54%) reported AEFI. Local reaction was the most frequently reported AEFI (112 person times in 90 participants) and the majority (64.29%, 72/112 person times) of the local reactions was pain at the injection site. Of the 90 participants reporting AEFI, 58.89% (n = 53) had their adverse events spontaneously improved one or two days after the vaccination. Totally 46 person times of systemic reactions were reported by 38 participants, and 32.61% (15 person times) of the systemic reactions was fatigue; the reported systemic reactions also spontaneously improved in 21 (55.26%) of the sufferers one or two days after the vaccination. There were 6 participants reporting both local and systemic reaction. No significant association of hypertension, diabetes and hyperlipidemia with the occurrence of AEFI was observed. There was a significant difference in the incidence of AEFI among the participants having different booster immunization schedules (χ² = 14.705, P < 0.05). Among the participants having inactivated vaccines, the incidence of AEFI was 12.59% (36/286) for those with the booster dose of homologous vaccine from the same manufacture as their routine vaccination and the incidence was 9.50% (67/705) for those with the booster dose of homologous vaccine but from different manufacture; among the participants having two doses recombinant novel coronavirus vaccine (type 5 adenovirus vector, abbreviated as adenovirus) the AEFI incidence was 13.33% (2/15); among the participants having non homologous vaccine booster dose, the AEFI incidence was 22.41% (13/58) or 4.30% (4/93) for those with the booster dose of adenovirus vaccine or recombinant novel coronavirus vaccine (CHO cell vaccine).

  Conclusion  The incidence of AEFI was lower in the elderly after receiving booster dose of COVID-19 vaccine with different immunization schedules and most of the AEFI were transient, self-limiting reactions, indicating a good safety of booster immunization of COVID-19 vaccine .