Mixed and Matched Covid-19 Vaccination in Saudi Arabia: Adverse Effects, Hospitalization, and Infection

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Hind Alzuraiq, Saleh Almutairi, Abdullah Alamri, Wafa Alanazi, Jaber Asiri, Shoog Almutairi, Sumaya Alkhawajah, Noor Alhabeeb


Vaccination has been conserved as an essential mechanism in the fight against SARS-CoV-2. Preliminary data have demonstrated that both the Pfizer–BioNTech and the Oxford–AstraZeneca vaccines have been significantly effective in reducing the number of COVID-19 infections and protecting older persons from severe disease.

The study aimed to investigate mixed and matched COVID-19 vaccination (Pfizer–BioNTech and Oxford–AstraZeneca) in terms of adverse effects, hospital admissions, and COVID-19 infections post-vaccination in Saudi Arabia.

An observational, analytical, cross-sectional, community-based study was conducted in Saudi Arabia within the period July–December 2022, and it included adult participants who received either two doses of the AstraZeneca or two doses of the Pfizer COVID-19 vaccines and who received one dose each of the AstraZeneca and the Pfizer vaccines. Data were collected via direct interviews using an interactive web-based interview system with an electronic version of the questionnaire after obtaining participant consent. Ethical guidelines and permissions were obtained from the relevant authorities, and data were collected, prepared, and analyzed using the SPSS software version 28.0

This study covered 424 adult participants with a mean age of 38.6 ± 16.4 years and a male-to-female ratio of 1:2.8. More than half of participants (243, 57.3%) were obese, while 60 (14.2%) were smokers and 63 (14.9%) had comorbidities, such as respiratory disease (29, 46%) and endocrine disorders (12, 19%). Concerning the vaccination regimen, the result  revealed that of the 311 participants (73.7%) who received two doses of the same vaccine, 262 (61.8%) received the Pfizer vaccine and 49 (11.6%) the AstraZeneca vaccine, while 113 (26.7%) received a mix (one dose each of the Pfizer and AstraZeneca vaccines). In total, 362 (85.4%) reported post-vaccination symptoms, such as body pains (208, 57.5%), muscle pain (207, 57.2%), and headaches (180, 49.7%). Nearly half (178, 49.2%) reported a symptom duration of 1–3 days, while hospitalization was reported in 10 (2.4%), ICU admission in 1 (0.2%), and COVID-19 infection post-vaccination in 63 (14.9%). The analysis found that symptoms were significantly higher among participants who received a mix of vaccines, compared with the participants who received two doses of the same vaccine (94.7% versus 82% respectively, and p = 0.001). Thus, the occurrence of symptoms was significantly higher among participants who received a mix of vaccines, compared with the participants who received two doses of the Pfizer or the AstraZeneca vaccine (94.7%, 82.8 and 79.6%, respectively and p = 0.004). Further, there was no significant effect between the vaccine regimen and the rate of hospitalization or COVID-19 infection post-vaccination (p values > 0.05 in all).

The study concluded that symptom occurrence after the second vaccination against COVID-19 was significantly higher among people who received one dose each of two different vaccines compared to those who received two doses of the same vaccine (Pfizer or AstraZeneca), though the rates 

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