Sinovac Real World Data Shed Fresh Light On China COVID Vaccine Efficacy Debate
New Strategies Needed?
Executive Summary
New real world data for Sinovac’s COVID-19 vaccine from hard-hit Brazil could fuel fresh doubts over the efficacy of Chinese vaccines, but also raise the urgency to change current vaccination strategy.
A new real world study, conducted from 19 January to 25 March 25, reviewing the efficacy of the CoronaVac vaccine from Sinovac Biotech Ltd., a Beijing-based developer, could fuel fresh doubts about the effectiveness of Chinese COVID-19 vaccines.
The study, unveiled on 7 April by preprint website MedRXIV.com and not peer-reviewed, focused on the region of Manaus, an Amazonian city that has seen the pandemic spread out of control in a country already hard-hit by the virus.
Previous study results for CoronaVac have shown a protection rate of 50.7%. The latest results, entitled “Effectiveness of CoronaVac in the setting of high SARS-CoV-2 P.1 variant transmission in Brazil: A test-negative case-control study”, are from a “matched test-negative case-control study to estimate the effectiveness of an inactivated vaccine” on local Brazilian health workers.
They show that “vaccination with at least one dose was associated with a 0.50-fold reduction (adjusted vaccine effectiveness, 49.6% 95% CI, 11.3 - 71.4) in the odds of symptomatic SARS-CoV-2 infection during the period 14 days or more after receiving the first dose,” noted the authors.
The roughly 50% protection rate seems to reinforce recent controversial comments from China’s top infectious disease official, Gao Fu, who said that protection is “not high” for Chinese COVID-19 vaccines in general.
Both Sinovac’s CoronaVac and two previously China-approved vaccines, from state-owned Sinopharm Group Co. Ltd., are based on an inactivated virus platform, a mature technology commonly used in China but not in western countries.
“It’s factual that COVID-19 vaccines based on an inactivated virus have lower efficacy than other vaccines, given results from multiple studies,” noted blogger Zhou Yebin of popular Chinese social media portal WeChat-based The Intellectual.
There had already been murmured doubts about the efficacy of Chinese COVID-19 vaccines, but Gao’s comments, as well as the latest data from Brazil seem to show the low protection rates are confirmed.
New Strategies Urged
The latest data also raise the urgency of changes to current vaccination strategies to offer better protection.
“There could be a need to get an additional shot when the newer vaccines become available,” suggested Ke Wu, CEO of Chinese domestic vaccine developer BravoVax, who spoke to Scrip in an earlier interview.
Such newer vaccines are being developed using more modern technologies such as mRNA and recombinant proteins. This in turn is providing an opening for smaller, more nimble companies such as Clover Biopharmaceuticals, Inc., which is progressing a recombinant protein-based adjuvant vaccine in a Phase II/III trial.
The Chengdu-based biotech has partnered with Dynavax Technologies Corporation to conduct the trial in Latin America.
A Chinese domestically-developed mRNA-based candidate is also in clinical trials and could be ready by year-end, noted one industry expert quoted in Hong Kong's South China Morning Post.
Gao, the director of China's Centers for Disease Control, said in his public comments that two remedies for limited vaccine efficacy were already under consideration.
One is to prioritize dosing procedures - increasing the number of shots, changing dosing and lengthening the waiting time between first and second shots. Some initial results have shown that a longer interval than the current two weeks between jabs may provide better protection.
The second approach under Chinese government consideration involves mixing vaccines that use different technologies, a strategy often referred as sequential inoculation. This approach is already being investigated in clinical programs in some western countries.
But ultimately, China must develop its own COVID-19 vaccines using the latest technology, namely mRNA, Gao stressed.
Despite the apparently low efficacy of CoronaVac in the Brazil study, the authors still called for increased vaccination, pointing to efficacy against SARS-CoV-2 virus and in particular the P.1 variant strain spreading in the country.
“Administration of at least one dose of CoronaVac showed effectiveness against symptomatic SARS-CoV-2 infection in the setting of epidemic P.1 transmission, underscoring the need to increase vaccination efforts in response to the spread of this variant in Brazil and globally,” they concluded.