Comparison of AstraZeneca and Sinopharm vaccines as boosters in protection against COVID-19 infection

Acute respiratory tract infections are common across all ages and genders, with a history of severe and persistent viral outbreaks. Coronaviruses, belonging to the Coronaviridae family, are enveloped, single-stranded RNA viruses with a genome among the longest of positive-polarity RNA viruses. Their primary evolutionary reservoirs are bats, and they can infect various animals. The subfamily Coronavirinae is categorized into four genera (α, β, γ, and δ-coronaviruses), with α and β genera infecting humans. Human coronaviruses, including SARS-CoV-2, primarily transmit via respiratory droplets, although other transmission routes have been observed. SARS-CoV-2, emerging in Wuhan, China, rapidly spread globally, causing a range of respiratory illnesses. The virus continues to mutate, with some mutations causing global concern, such as the Omicron variant, known for its high number of mutations and transmissibility. In response to the pandemic, the WHO implemented various strategies, with vaccination ultimately deemed the most effective approach. Numerous vaccines have been developed using different platforms (inactivated, live attenuated, recombinant protein, vectored, and mRNA-based). The Sinopharm (BBIBP-CorV) vaccine, an inactivated vaccine, and the AstraZeneca (ChAdOx1 nCoV-19) vaccine, a recombinant adenovirus-vectored vaccine, are two examples of vaccines used globally. Both have shown efficacy in clinical trials, though AstraZeneca demonstrated some safety concerns in certain populations regarding thromboembolic events. The use of combination vaccines has been explored for potentially superior immune response. This study investigates the efficacy of using Sinopharm or AstraZeneca as a booster dose after two initial doses of Sinopharm, focusing on symptom severity in individuals who still contracted COVID-19.

The introduction extensively reviews the history of viral respiratory infections, the characteristics of coronaviruses, the emergence and spread of SARS-CoV-2, including the Omicron variant, and the global response, focusing on vaccination strategies. It details the development and characteristics of both the Sinopharm and AstraZeneca vaccines, highlighting their mechanisms of action, efficacy rates from clinical trials, and reported side effects. Existing literature suggests the potential benefits of using different vaccines in a combination approach, a strategy also discussed in the context of the current study.

This cross-sectional study involved 346 patients with respiratory symptoms referred to Besat Hospital between February and April 2022. 120 patients tested positive for SARS-CoV-2 via real-time PCR and had received a full three-dose vaccination regimen. The study focused on 94 of these patients who had received two doses of the Sinopharm vaccine followed by either a third Sinopharm dose or an AstraZeneca booster dose. Nasal and nasopharyngeal swab samples were collected and processed using the High Pure RNA Isolation Kit (Roche) and a one-step real-time PCR mastermix for SARS-CoV-2 RNA detection (Qiagen rotor-gene q). The data collected included age, gender, and the type of vaccine received for each dose. Patients were divided into age groups (18-30 years and 30-50 years) and vaccine groups (three doses of Sinopharm (SSS) or two doses of Sinopharm and one dose of AstraZeneca (SSA)). Symptom data (body aches, sore throat, runny nose, fever, shivering, cough, fatigue) were collected and analyzed. Categorical variables were summarized using n (%), and differences between groups were compared using the χ2 test or Fisher's exact test. Statistical significance was set at α < 0.05, and analysis was performed using R version 4.1.3.

The study included 94 patients with confirmed COVID-19 infection after receiving three vaccine doses. The patients were divided into age groups (18-30 years and 30-50 years) and vaccination groups (SSS and SSA). The results indicated that in the 18-30 age group, individuals receiving the SSA vaccination regimen (two doses of Sinopharm and one dose of AstraZeneca) experienced fewer symptoms compared to the SSS group (three doses of Sinopharm). Specifically, the SSS group showed an 8.2% increase in fatigue and a 4.1% increase in fever compared to the SSA group within this age range. Similar trends were observed in the 30-50 age group, with the SSA group showing a lower prevalence of various symptoms than the SSS group. The provided figures (Figure 3) details the precise number of individuals reporting each symptom for each age and vaccination group. Statistical analysis using Pearson's Chi-squared test demonstrated a significant difference between the groups concerning various symptoms (p-values ranged from <0.001 to 0.034). These findings suggest that the AstraZeneca vaccine, when used as a booster after two doses of Sinopharm, may be more effective in reducing the severity of COVID-19 symptoms compared to receiving three doses of the Sinopharm vaccine.

The study's findings highlight the potential benefit of heterologous boosting with the AstraZeneca vaccine following Sinopharm vaccination in reducing COVID-19 symptom severity. This aligns with previous research suggesting that mixing and matching vaccines might be more effective than using the same vaccine for all doses. The reduced symptom severity observed in the SSA group suggests a potential advantage in terms of preventing severe disease and improving patient outcomes compared to the SSS group. These findings add to the growing body of evidence on the importance of booster doses and the potential efficacy of vaccine mixing strategies. However, further research is needed to confirm these findings and explore the long-term effects of different vaccine combinations. The study's limitations should be considered when interpreting the results.

This study demonstrates that a heterologous booster dose of AstraZeneca after two doses of Sinopharm may result in fewer COVID-19 symptoms compared to a homologous booster of Sinopharm. This suggests potential benefits of vaccine mixing strategies. Further research should investigate different vaccine combinations, including exploring fully immunized groups with only AstraZeneca vaccine, to determine optimal vaccination strategies for stronger immunity against COVID-19.

The study is limited by its cross-sectional design, which restricts inferences about causality. The relatively small sample size and the focus on a specific vaccination history might limit the generalizability of the findings to other populations or vaccination regimens. The lack of information on other relevant factors (sex, occupation, place of residence) might have influenced the results. The study only evaluated symptoms and not more objective outcomes like hospitalization or mortality rates.