This ambispective cohort study announces infection rates with confirmed COVID-19 among a large Egyptian health care workers (HCWs) cohort (n = 1228) for 7 months follow up (March 2021, to September 2021). We identified 18 cases of COVID-19 (5.5%) among vaccinated HCWs with an incidence rate ratio of 0.39 (95%CI, 0.24–0.65). We observed that inactivated BBIBP-CorV vaccine (Sinopharm) had an efficacy of 67% among healthcare workers calculated as a percentage of (1- adjusted HR).
Our study has at least three main strengths. First, it was conducted across multi-centers distributed all over Egypt; fifteen hospitals were included chosen by multistage sampling technique_ the highest infection rate areas. Second, we targeted health care workers as they are the theater of war in this pandemic disease, exposed to high viral load. Third, we also handled a subgroup analysis for all variables for our outcomes.
The Emergency authorization handed out the inactivated whole virion vaccine (BBIBP-CorV), it was the initial launch of a vaccination program against COVID-19 for HCWs that began on January 16, 2021. The Sinopharm vaccine was not as effective against variants of SARS-CoV-2 as the original virus(15). However, our timeline study could ensure its efficacy against Delta variant_ the second surge linked to highly transmissible Delta variant. On the 28th of July 2021, appears in 132 countries globally. Moreover, WHO Eastern Mediterranean Region Office reported detection of Delta variants in 15 countries including Egypt(16). The Egyptian Ministers of Health announced the first Delta variant case in Egypt in July(17). This variant is a predominant one till now in Egypt(18). Consequently, the first detection of this variant in India from March 2021(19), did not block its appearance before in Egypt. Hence, our targeted population in their hospitals deals with all COVID-19 patients, they may be infected by existing variants during the follow-up period.
Moreover, there was a statically significant difference between the 2 groups in the number of workdays lost due to COVID-19 infection, days were greater in the unvaccinated group that certainly will impact the provision of health services and consequently economically effective. Also, the vaccine effectiveness (VE) for hospitalization or mechanically ventilation due to COVID-19 infection was insignificantly between two arms, that is maybe due to the good planning and innovation in public health to control the infection outbreak _Egyptian protocol management, less severe new variants of the virus, our median age groups.
The VE in our study are similar to estimates that have been reported in New Delhi, India for SARS-CoV-2 reinfection rate and estimated effectiveness of the inactivated Whole Virion Vaccine BBV152 among Health Care Workers, Fully vaccinated HCWs had a lower risk of reinfection (HR = 0.14, 95%CI 0.08–0.23)(20). Despite their higher VE, and that is maybe due to their larger sample size or different vaccine type, their study was conducted at only one large hospital. In addition, a randomized double-blind phase 3 trial in the United Arab Emirates (UAE) and Bahrain to evaluate the efficacy and adverse events of 2 inactivated COVID-19 vaccines interpreted significantly decreases symptomatic COVID-19 risk, and sentinel AEs were rare(21). However, the limitations of this study: it was conducted in a healthy population and the efficacy among those with chronic disease, older adults, and those with previous SARS-CoV-2 infections were not sufficiently reported; also, Egypt and Jordan data were not included in the interim analysis and final analysis not reported yet.
From the previous studies, the inactivated Sinovac vaccine efficacy in Brazil was found 51% for symptomatic COVID-19 infection(22), with longer dosing intervals, while in Turkey was found 83.5% efficacy(23) and in Indonesia reported 65% efficacy(24). Although the inactivated vaccine was not as effective against variants of SARS-CoV-2 as the original virus, the vaccine effectiveness was still over 50% for fully vaccinated people(15). Till now, the available data suggests that effectiveness is highest in RNA vaccines than viral vector ones and the least in the inactivated SARS-CoV-2 vaccines. However, Israel recently reported a breakthrough infection of SARS-CoV-2, dominated by variant B.1.1.7 in a small number of fully vaccinated health care workers, raising concerns about the effectiveness of the original vaccine against those variants(25). Whereas, another study in Egypt shows that the Sinopharm vaccine cannot trigger sufficient antibodies as an immune response in most vaccinated cases(15). The UAE solved this problem by a third booster dose of the Sinopharm vaccine to improve antibody response. Subsequently, more studies are needed in those who receive three doses of the Sinopharm vaccine to determine the vaccine's effectiveness among them. On the other hand, we adjusted for previous COVID-19 infection _ before 14 days after fully vaccinated in the vaccinated group and before 1st March for the unvaccinated group_ to encompass high titers of immune antibodies and we did not find any difference. Indeed, another study examined one of COVID-19 vaccine effectiveness with influenza vaccine to assess immunogenicity(26). So, we adjust this variable in our study, and no difference between the two groups.
The vaccine works by using killed viral particles to expose the body's immune system to the virus without risking a serious disease response(15). In our study, the post-vaccine symptoms after the first and second doses are commonly mild, as classified by the participants. About half of the participants developed local mild reactions and local pain. Fever was also mild and was the highest following the 1st dose only- 34.2% - with the highest temperature 39°C- with a maximum of 3 days. Similar to the findings of an earlier study, it is noticeable that a higher percentage of participants did not feel any side effects after the second dose of vaccination than after the first dose(27), which may be attributed to the immune system response (increase cytokines). Other adverse events were variable and mostly occurred in one patient, mild Edema face hand, hypertension, and hypotension.
After all that, there is hesitancy in accepting vaccination among people, accepted mainly by young HCWs with fewer comorbidities and risk factors for admission. Our study supports the governmental efforts to improve vaccination coverage and impose it for people in many sectors. Finally, the vaccination against SARS-CoV-2 is the solution to overcome this disaster infection.
This study is observational so the causal relationship between adverse events and vaccine administration could not be well defined. We need further studies for other categories of populations like children, pregnant and lactating women to check for efficacy and safety of this vaccine among them and for a longer duration. In addition, we may miss some asymptomatic patients during the follow-up period.