Three novel coronaviruses, Coronavirus Associated Severe Acute Respiratory Syndrome (SARS-CoV), Middle East Respiratory Syndrome Coronavirus (MERSCoV), and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is a human-to-human transmitted and global pandemic disease 1. SARS-CoV-2 is an enveloped single-stranded positive-sense RNA virus that caused the pandemic of coronavirus disease 2019 (COVID-19) and resulted in millions of deaths across the globe 2. The genome of SARS-CoV-2 is almost 30 kb which encodes major structural proteins, including spike (S) protein and accessory proteins (ORF 3a, 6, 7a, 7b, 8, and 10) 3. The S protein is essential for the life cycle of SARS-COV-2 and is considered a major target antigen for vaccines against the virus. In the host cells, the spike protein is cleaved into S1 [Receptor-Binding Domain (RBD)- containing] and S2 (non-RBD-containing) subunits 4.
In most communities, Healthcare workers (HCWs) are exposed to the virus at a greater level than any other society members and may be considered at an elevated risk of infection. Their role in the chain of transmission is essential, through which they help control and prevent the spread of COVID-19 disease 5.
Various forms of vaccine candidates targeting SARS-CoV-2 are classified as inactivated virus vaccines (Sinovac Biotech, Beijing, China; Sinopharm Beijing Institute of Biotechnology, Beijing, China; Bharat Biotech, Hyderabad, India), Ad26- based vector vaccine (Janssen/Johnson & Johnson, Titusville, NJ, USA), the chimpanzee adenovirus vector vaccine (AstraZeneca, Cambridge, UK/Oxford University, Oxford, UK), Ad5 and Ad26-based vector vaccine (Gamaleya, Moscow, Russia), protein subunit based vaccines (Novavax), and mRNA vaccines (Moderna, Cambridge, US/NIAID, MA, USA; Pfizer, New York, NY, USA/BioNTech, Mainz, Germany) 6,7.
COVID-19 vaccinations induce adaptive protective immunity, including specific T cell and B cell antibody responses 8. Specific antibodies such as IgM, IgG, and IgA mainly bind to the spike protein and can neutralize the fusion and entry of SARS-CoV-2 to the host cell. Therefore, these antibodies form the 'immunological memory' and could aid in preventing the potential COVID-19 virus. The serum concentrations of these antibodies can be analyzed to assess the efficiency of different types of vaccines 9, in this research. We aimed to examine and compare the efficiency of Sputnik, AstraZeneca, and Sinopharm in terms of the amount of antibody produced and the correlation of antibody response with age, sex, and history of corona disease in professors, students, and staff of Shahid Beheshti School of Dentistry and employees of Shahid Beheshti University of Medical Sciences.
Due to the fact that the response of the immune system in different races and human populations is diverse, therefore, conducting this study in an acceptable population in Tehran emphasizes the importance of the work and its novelty.
COVID-19 is still an ongoing global pandemic, and the world needs to be immunized against the virus with a vaccine to bring this pandemic to an end 10. Following SARS-COV-2 infection, adaptive immunity generates the receptor binding domain neutralizing antibodies of the spike protein and nucleocapsid protein. In addition, most COVID-19 vaccines trigger neutralizing antibodies specific to the spike protein 11. Vaccination is considered a crucial strategy to control viral infections 12. Corona vaccines use structures similar to the spike protein of the virus. They prepare the immune system to identify the virus 13,14. In glycoprotein S, there is a place called the Receptor Binding Domain (RBD) through which the virus binds to its receptor on the host cell's surface 13-15. Changes in this region are primarily responsible for binding to the Angiotensin-converting enzyme 2 (ACE2) receptor 15.
To measure the level of immunity obtained from corona vaccine, the amount of specific IgG antibodies in the blood is checked 16-18. Neutralizing antibodies cause changes in the spike protein structure and the IgG antibody specifically targets the S1 subunit of the S protein and the RBD. According to the findings of this study, the amount of IgM and IgG antibodies produced as a result of vaccination was the highest in AstraZeneca, but there was no significant difference and the type of vaccine had no significant effect on the amount of antibodies. The amount of IgM and IgG antibodies produced by vector-based vaccines, AstraZeneca and Sputnik, is higher than the Sinopharm vaccine, produced using inactivated virus technology. A study showed that the amount of specific anti-spike IgG produced after the injection of AstraZeneca and Sputnik V vaccines was almost the same 19. Another study showed that the performance of the Sinopharm vaccine in creating anti-spike IgG is weaker than AstraZeneca and Sputnik vaccines 20. According to the results of another study compared to AstraZeneca and Pfizer vaccines, Sinopharm and Sputnik V vaccines produced lower amounts of antibodies and had lower anti-RBD-ACE2 activity 21,22.
According to the results of this study, the amount of IgM and IgG antibodies produced as a result of vaccine injection was equal in both sexes, and no statistically significant difference was observed. A study showed no meaningful relationship between gender and IgG titer after vaccination in any Sinopharm and AstraZeneca vaccines 21. Another study showed no statistically significant difference in IgG antibody titer in men and women who received AstraZeneca and Sinopharm vaccines 23.
This study observed no clear and significant pattern between age and the amount of IgM and IgG antibodies produced, including a linear relationship. A negative correlation between age and neutralizing IgM antibodies was shown in a study regarding Sinopharm and AstraZeneca vaccines 23. Another study showed that the amount of anti-COVID IgG antibody produced was similar in adults aged 19 to 24 who received the AstraZeneca vaccine, but the titer of SARS-CoV-2 anti-spike IgG was lower in people over 60 receiving this vaccine 24,25.
Individuals with a history of corona disease are expected to have a more robust antibody response after vaccination 26. This study has shown that the history of infection with COVID-19 within six months before the measurement of antibodies increased the antibody response. This increase in response was significant for the AstraZeneca vaccine, but not significant for the other two vaccines. For all three vaccines, the average amount of IgM and IgG antibodies was higher in people with a history of corona disease than those who did not have an account of this disease. This difference in the amount was more remarkable for people from this study who received two doses of the AstraZeneca vaccine than those who received two doses of the Sinopharm and Sputnik vaccines. A study showed that the history of corona disease significantly affected neutralizing antibody titer and IgG antibody titer in both types of AstraZeneca and Sinopharm vaccines 27.
