A NEW Bahrain study has reiterated that getting inoculated against coronavirus (Covid-19) is an effective strategy to reduce the risk of infection and its consequences, especially among the elderly.
However, the research, titled ‘Morbidity and mortality from Covid-19 post-vaccination breakthrough infections in association with various Covid-19 vaccines and the emergence of variants in Bahrain’, also noted that the Sinopharm vaccine appeared to be less effective in older Covid-positive vaccinated individuals.
Based on vaccinated data between December 9 and July 17, the paper published by Research Square, said compared to Pfizer/BioNTech vaccine recipients, individuals vaccinated with Sinopharm had a higher risk of the four outcomes – post-vaccination infections, hospitalisations, intensive care unit (ICU) admissions and deaths, especially in those aged above 50.
It added that the Sinopharm vaccine was deployed at an approximately three-fold higher rate compared to the Pfizer/BioNTech vaccine, citing the possible “oversampling of individuals” who received the Sinopharm vaccine and experienced the outcomes.
The study – co-authored by four members of the National Taskforce to Combat the Coronavirus (Covid-19), including its monitoring committee head Lieutenant Colonel Dr Manaf Al Qahtani – primarily addressed two critical questions: The effectiveness of various vaccines and the magnitude and clinical consequences of post-vaccination infections amidst emerging variants, especially the Delta variant.
“Bahrain’s decision to deploy four vaccines provided an unparalleled opportunity to examine and directly compare the effectiveness of different vaccines in (outcomes) over time in a large population as new variants were emerging,” said the study.
The kingdom has deployed four vaccines free of cost to the eligible individuals out of an estimated 1.5 million population – Sinopharm, Pfizer/BioNTech, Astra-Zeneca and Sputnik V.
During the study period which covered 1,003,960 vaccinated individuals, 569,055 had received Sinopharm, 184,526 Sputnik, 73,765 AstraZeneca and 176,614 Pfizer/BioNTech.
Additionally, 245,876 individuals were used as the unvaccinated case-control unit which included travellers, asymptomatic and symptomatic contacts of those who had tested positive and others, excluding those aged 12-17.
“We conclude that the four vaccines were effective in reducing all four outcomes in vaccinated compared to unvaccinated individuals, prior to, and during the period when the Delta variant became dominant in the country (May 2021 to the present),” said the study.
“However, in a pairwise comparison, the performance of the Pfizer/BioNTech vaccine was superior to the Sinopharm vaccine, especially in older individuals and in the context of the emergence of the Delta variant.”
The study endorsed that vaccination offers a “critical tool” to control the pandemic, especially with the advent of the Delta variant, adding that the findings supported “the urgent need to expand vaccination access around the world” as it could serve to guide the choice of vaccines in the context of the Delta variant.
Bahrain rolled out Sinopharm (after conducting a three-phase clinical trial locally with 7,700 participants) on December 9 followed by Pfizer/BioNTech on January 30, AstraZeneca on March 13 and Sputnik V on March 4.
According to the analysis the median age of individuals vaccinated was similar across the four vaccines: Sinopharm – 38 years, AstraZeneca – 39 years, Sputnik V – 35 years and Pfizer BioNTech – 36 years.
However, it varied gender-based: Pfizer/BioNTech – 63.4pc males/36.6pc females, Sinopharm – 60.9pc males/39.1pc females, Sputnik V – 73.4pc males/26.6pc females, and AstraZeneca – 81.9pc males/18.1pc females.
Among the other outcomes, the study identified 180,840 polymerase chain reaction (PCR) positive cases with 134,728 aged 18 and above. There were 13,105 hospitalisations, including 1,636 ICU admissions, and 1,030 deaths.
An analysis on deaths by vaccination status on those aged above 18 was also done on groups paired between the unvaccinated and the four vaccines. The per cent of deaths among all Covid-19 cases in unvaccinated people aged above 50 was 3.8-fold higher compared to the Sinopharm, and approximately 7.5-fold higher than the Sputnik V vaccine recipients.
Gender-wise demographics of the four vaccines in Bahrain
There were no deaths reported in the AstraZeneca vaccinated group.
In patients aged below 50, the percentage of deaths among all Covid-19 cases in unvaccinated people were 8.1-fold higher compared to Sinopharm vaccine recipients. There were no deaths reported in this age cohort in Sputnik V and Pfizer/BioNTech vaccine recipients, and one death among the AstraZeneca vaccine recipients.
The death rate among all PCR positive post-vaccination Covid-19 cases among recipients of the Sinopharm vaccine was 0.46pc (112 deaths) versus 0.15pc for Pfizer/BioNTech (three deaths) and 0.03pc for AstraZeneca (one death).
“This trend was consistent for all Covid-19 events – infection, hospitalisation, ICU admission and death,” it added.
Other authors of the study included task force members Dr Abdulla Alawadi, Dr Hamad Al Mahmeed and Dr Jaleela Al Sayed; Dr Sujoy Bhattacharyya from Columbia University’s Economics Department, professors Dr Jessica Justman and Dr Wafaa El Sadr from the university’s Mailman School of Public Health, assistant professor Siddhartha Mukherjee from the university’s oncology division and Alphabet, Mountain View lead researcher Jack Hidary.