Adverse Effects Following the First and Second Dose in Individuals Receiving the Pfizer/BioNTech COVID-19 Vaccine: A Cohort Study

Abstract

The FDA-approved vaccine against the novel coronavirus developed by Pfizer and BioNTech became widely popular in Iraq. The study aims to evaluate the incidence of vaccine adverse reactions, and severity after first and second doses and to link some of the demographic criteria of recipients. This study included 850 adults (16 years and older), and the sample was collected from a randomly selected vaccination center in Baghdad, Iraq for the period January to March 2022. Study Participants were directly interviewed while taking the first dose. Later on, phone calls were used to monitor participants’ self-reported local or systemic adverse reactions for one week after the first dose and second dose. The participants’ age range was (19-76 years) with a mean of (46.2 ± 15.8) years. 59.9% were males. The mean body mass index (BMI) was (27.7 ±2.9). The incidence of vaccine adverse reactions after first and second doses were: first dose (local 17%, systemic 27%), second dose (local 27%, systemic 35%). Ordinal logistic regression analysis after adjusting for age, sex, and past medical history (PMHx) showed a higher incidence and severity in females and those with PMHx in nearly all the types of reactions except for chills (second dose) and PMHx (two doses), muscle or joint pain (two doses). Spearman’s Rank test showed an insignificant correlation with any type of reaction. The vaccine is generally safe and adverse reactions are mild and tolerable in the majority of cases.