Currently, vaccines are the best strategy for protection against covid-19 infection. After the Covid-19 outbreak several types of vaccine with different formulations were introduced and received by billions of people around the world. Induction of a protective immunity by vaccines depends not only on host factors but also vaccine components and structure so it is necessary to evaluate the efficacy of different vaccines among people with different socio-economical and genetic backgrounds. In the current study the rate of IgG seropositivity after receiving two doses of four different vaccines was evaluated in a group of participants. The Sputnik V vaccine which invented by Gamaleya Research Institute (Russia), has the gene of the SARS-CoV-2 glycoprotein S. The 1st and 2nd doses of Sputnik V vaccine use two different types of adenoviruses as carriers of the spike gene; rAd26 and rAD5 for the first and second doses, respectively. Phase 1/2 clinical trials showed that both formulations of this vaccine were tolerable and safe [28]. “ChadOx1-nCoV-19” or AZD-1222 composed of the replication-deficient simian adenovirus vector, which contains the sequence of the spike protein. According to studies, this vaccine is more tolerable in the elderly, and after a booster dose, it creates an equal immunity in all age categories [28]. “BBIBP-CorV” or Sinopharm vaccine is an inactivated whole virion which is produced by the Beijing Institute of Biological Products and the state-owned Chinese company Sinopharm. It induced high levels of neutralizing antibody in six mammalian species, which can protect them against SARS-CoV-2 infection [29]. “BBV152” or Covaxin is an inactivated whole SARS-CoV-2 virion particle, which is produced by Bharat Biotech Company. This vaccine formulated with a toll-like receptor 7/8 agonist molecule adsorbed to alum. The Covaxin vaccine was developed using the NIV-2020-770 strain (obtained from an Indian patient with COVID-19), has acceptable safety and can effectively elicit cellular and humoral responses [28].
According to the results, Sputnik V and AZD-1222 vaccines are more effective than Sinopharm and Covaxin vaccines. This may be due to differences in the platform of these vaccines [21]. The platform used in Sputnik V and AZD-1222 vaccines is a live viral carrier, which according to previous studies has a high ability to stimulate the immune system [5, 24]. In contrast, the platform used in Sinopharm and Covaxin vaccines is inactive viruses that have less ability to stimulate the immune system [29, 30]. The immunogenicity of Sputnik V and AZD-1222 vaccines was estimated to be about 90%, which is consistent with similar studies [31, 32]. Also, the effectiveness of Sinopharm and Covaxin vaccines was about 70%, which was consistent with most studies [30, 32]. Regarding the effect of age on vaccine efficacy, the results varied depending on the type of vaccine. The efficacy of the vaccine and the production of neutralizing antibodies in the Sputnik V and AZD-1222 vaccines were significantly higher in participants under 50 years old. However, in people who received the Sinopharm or Covaxin vaccine, the production of neutralizing antibodies did not differ significantly between the two age groups. Given that the platform of Sputnik V and AZD-1222 vaccines is a type of live viral vectors, it seems that the use of this platform has different effects between male and female [15].
Also in another study, Voysey et al., determined AZD-1222 vaccine efficacy in the UK, and vaccine efficacy was 95.8%. Their result was similar to ours (93%) [33]. Ewer et al. determined the antibody responses induced by AZD1222 vaccine in adults (Mean age: 18–55), up to 8 weeks after vaccination. Robust immunity induced against the spike antigen, determined by total IgG ELISA. In their studies, no relationship was found between age and the magnitude of immune response. Anti-SARS-CoV-2 antibody were measurable at day 14 and peaked at day 28 [34]. In another study Wall and colleagues assessed AZD1222-induced neutralizing antibody against SARS-CoV-2 Delta variant of concern. Two doses of AZD1222 produced neutralizing antibody against the wild type strain in all participants (100%). Moreover, 95% and 87% individuals had a measurable neutralizing antibody against the B.1.1.7 and D614G variants, respectively. [35]. Jeewandara et al., measured immune responses to a single dose of the AZD1222 vaccine in health care workers. 93.4% of participants were positive for neutralizing antibody production, regardless of gender and age. Hemagglutination tests for antibodies to the RBD were done in a sub-cohort, and ACE2 blocking antibodies were detected in 97.1% of naive persons [36]. Moreover, Wall et al., investigated the ability of AZD1222 vaccination to elicit neutralizing antibodies against SARS-CoV-2 (Delta) in 106 participants. According to result, 87% of individuals had a measurable neutralizing antibodies against the B.1.1.7 and D614G variants, but only 62% of participants had quantifiable NAbTs against B.1.617.2 (Delta variant) following two doses of AZD1222 [37].
In a study by Logunov et al., Sputnik V vaccine efficacy was determined among adult participants. Vaccine efficacy in this study was 92%, which was very similar to our study (95%) [24]. Moreover, in a study by Claro et al., they assessed the antibody (IgG) response against the RBD of the spike protein and the Nucleocapsid protein (NP) in Venezuela, after the vaccination by Sputnik V. Antibody responses against RBD and nucleocapsid protein were measured by ELISA. All of participants demonstrate a strong IgG immune response against RBD after the second dose, however only 58% of participants had an immune response after 1st dose [38]. In another study by Rossi and colleagues, among health care workers in Argentina, SARS-CoV-2 specific antibody responses were evaluated after vaccination by Sputnik V. IgG anti-spike titers and neutralizing capacity was determined after two doses, and 94% of participants developed spike-specific IgG antibodies. Interestingly, a single Sputnik V dose elicited higher antibody levels in previously infected individuals [39]. Also, Gushchin et al., evaluated neutralizing activity of sera from Sputnik V vaccinated subjects against variants of concern such as alpha variant. The data obtained indicated no significant differences in virus-neutralizing activity against alpha variant [40].
There are many studies on the effect of Sinopharm vaccine on the creation of neutralizing antibodies against SARS-CoV-2. Holt et al., performed a study to evaluate the antibody responses following vaccination with the Sinopharm vaccine in the UAE after two doses (1296 participants). The antibody responses were measured 14–21 days after the second dose by means of chemiluminescence immunoassay technology, and neutralizing antibody testing was carried out by a blocking enzyme-linked immunosorbent assay. According to result, 56% of participants had a positive anti-spike antibody against SARS-CoV-2, which is lower than the our result (73%) [41]. In another study by Jeewandara et al., the kinetics of immune responses following the Sinopharm/BBIBP-CorV was measured in Sri Lankan. SARS-CoV-2 specific total antibodies were evaluated in 83 individuals by ELISA, after the second dose. RBD specific antibodies were measured by ELISA, and about 95% of participants had measurable SARS-CoV-2 specific total antibodies in their study [42]. Moreover, Ferenc and colleagues, determined virus neutralizing antibody responses after second dose of Sinopharm Covid-19 vaccine in 450 participants. Outcomes were examined in a multivariable model for gender and age. Similar to our study, gender was slightly correlation with the antibody titers, but antibody titers were highly correlated with age. Measurable antibody levels were detect in approximately 90% of subjects under 50 years of age, but production of the antibody was decreased sharply with age [43]. Nevertheless, in our study, age had no significant effect on the efficacy of the Sinopharm vaccine.
Various studies have been performed on the efficacy of the Covaxin vaccine. In a study by Ella, Covaxin vaccine efficacy was measured in Indian hospitals. Participants was followed two weeks after the second vaccination; and vaccine efficacy was reported 77.8%, which was similar to our result (70%) [30]. In another study by Singh et al., antibody response was determined after Covaxin (BBV-152) vaccine among 515 Health Care employees, in India. Anti-spike antibody titer was measured at day 21 after vaccination. The IgG to SARS-CoV-2 directed against the spike protein were assayed with indirect chemiluminescence immunoassay (CLIA). About 44% of participants showed seropositivity after vaccination, which is lower than our result (70%). Also similar to our study, no difference was observed with age and gender [44]. In a study by Kumar, antibody responses to the BBV152 vaccine were measured in healthcare professionals. Serological testing for anti-spike antibodies measurement was performed using chemiluminescence immunoassay. According to their results, about 76% of participants showed seropositivity after vaccination, which is higher than our result (70%) [45].
Finally, in another study, Covid-19 vaccine efficacy was done by Siddique and Ahmed in Pakistan. In this study, the efficacy of various vaccines including Sputnik V, AZD-1222 and Sinopharm vaccines was evaluated. The results showed that the efficacy of Sputnik V, AZD-1222 and Sinopharm vaccines was 92%, 70% and 79%, respectively, which compared to our study, the efficacy of the AZD-1222 vaccine has been less reported [46].