KUALA LUMPUR, Nov 24 — The effectiveness of Sinovac’s Covid-19 vaccine against intensive care unit (ICU) admission wanes faster over several months, falling from 55 per cent two months after receiving the two-shot series to 28 per cent about three to five months later.
The two-dose Sinovac vaccine’s efficacy against Covid-19 infection also fell to 28 per cent from 76 per cent over the same period, according to studies by the Real-World Evaluation of Covid-19 Vaccines Under the Malaysia National Covid-19 Immunisation Programme (RECoVaM) and the National Medical Research Register (NMRR).
In contrast, Pfizer’s two-dose Covid-19 vaccine remains 79 per cent effective at preventing ICU admission after three to five months from 86 per cent after the primary vaccination. In terms of protecting against Covid-19 infection, however, Pfizer’s vaccine efficacy declined from a peak of 89 per cent to 68 per cent over the same time frame.
The study further found that Sinovac’s Covid-19 vaccine was only 76 per cent effective against breakthrough deaths after three to five months, falling from 79 per cent two months after the primary series. In comparison, Pfizer’s Covid-19 vaccine remained 91 per cent effective against breakthrough deaths after five months.
Data provided by Dr Mahesh Appannan, head of data at the Ministry of Health’s (MOH) Crisis Preparedness and Response Centre (CPRC), showed that the death rate among those double vaccinated with Sinovac was the highest, compared to Pfizer and AstraZeneca.
Sinovac had a weekly adult death average of 2 per 100,000 population between June 7 and November 15, 2021, versus Pfizer’s weekly adult death average of 0.667 per 100,000 population, and AstraZeneca’s weekly adult death average of 0.25 per 100,000 population.
Unvaccinated deaths, however, dominated, with weekly adult deaths averaging at 22.354 per 100,000 population over the same 24-week period.
Covid-19 death data from November 1 to 20, 2021, collated by consultant paediatrician Dr Amar-Singh HSS showed that unvaccinated adults are 14.5 times more likely to die from the virus compared to those fully vaccinated.
Dr Amar arrived at the conclusion after tallying the 827 Covid-19 adult deaths reported over the 20-day period — 315 unvaccinated, 41 partially vaccinated, and 471 fully vaccinated — against the number of unvaccinated (1,031,946), partially vaccinated (526,632), and fully vaccinated (22,379,626) adult population. These figures are available on MOH’s GitHub repository.
The sum showed that the death rate among unvaccinated adults from November 1 to 20 is at a high 305.2 deaths per million population compared to 77.9 deaths per million people and 21.1 deaths per million people among the partially and fully vaccinated population, respectively.
Among the 471 fully vaccinated adult deaths recorded over the period, 332 were Sinovac recipients, 127 were double vaccinated with Pfizer, and 12 received two shots of AstraZeneca.
When compared against the population size by vaccine type, Dr Amar found that Sinovac’s breakthrough death risk is the highest among the three Covid-19 vaccines at 34 deaths per million people, compared to Pfizer at 9.8 deaths per million people and AstraZeneca at 6 deaths per million people.
Dr Amar noted that AstraZeneca’s Covid-19 vaccine risk may be biased by a younger population that received the vaccine.
The National Pharmaceutical Regulatory Agency (NPRA) on November 17 authorised the use of Sinovac and AstraZeneca Covid-19 vaccines as booster shots for adults aged 18 and older.
The NPRA’s conditional approval for homologous vaccination with Sinovac booster doses was issued amid hesitancy among double-vaccinated Sinovac recipients to get a different vaccine — Pfizer — for a third shot.
The MOH, however, highly recommends a Pfizer booster shot for individuals vaccinated with two doses of Sinovac, based on data from studies conducted in Thailand, Chile, and Turkey.
A real-world study in Chile found that administering Pfizer or AstraZeneca as a third dose for recipients double vaccinated with Sinovac’s Covid-19 vaccine was more effective than a third Sinovac jab.