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Sinovac Biotech CoronaVac’s experimental COVID-19 vaccine triggered a rapid immune response, but the level of antibodies produced was lower than in people who had recovered from the disease, the trial’s first results showed Wednesday.
Although the early and mid-stage trials were not designed to evaluate the efficacy of CoronaVac, the researchers said it could provide sufficient protection, based on their experience with other vaccines and data from preclinical studies with macaques.
The study follows encouraging announcements this month from US pharmaceutical manufacturers Pfizer and Moderna, as well as Russia’s Sputnik V, that their experimental vaccines were more than 90 percent effective based on interim data from large, late-stage studies.
CoronaVac and four other experimental vaccines developed in China are currently being tested at an advanced stage to determine their effectiveness in preventing COVID-19.
Sinovac’s findings, published in a peer-reviewed article in the medical journal The Lancet Infectious Diseases, are derived from the results of Phase I and II clinical trials in China involving more than 700 participants.
“Our results show that CoronaVac is able to induce a rapid antibody response within four weeks of immunization by administering two doses of the vaccine at an interval of 14 days,” said Zhu Fengcai of the Provincial Center for Disease Control and Prevention. of Nanking and one of the authors of the article.
CoronaVac is one of three experimental COVID-19 vaccines that China has used to inoculate hundreds of thousands of people as part of its emergency program. [File: Thomas Peter/Reuters]
“We believe this makes the vaccine suitable for emergency use during the pandemic,” Zhu said in a statement published alongside the document.
Among the limitations of the Phase II studies, the researchers noted that only healthy adults were involved and that the study did not include individuals from groups known to be more susceptible to COVID-19, including people aged 60 or older, or with other diseases. underlying.
It also did not evaluate T-cell responses, which they said would be part of the Phase III trials in Brazil. Phase III trials are also underway in Indonesia and Brazil, which have reported the largest number of coronavirus cases in the world after the United States and India.
The results of these large, late-stage studies would be crucial in determining whether the immune response generated by CoronaVac was sufficient to protect people from coronavirus infection, the scientists said.
Naor Bar-Zeev of Johns Hopkins University, who was not involved in the study, said the results should be interpreted with caution until the Phase III results are published.
“But even then, after Phase III trial is completed and licensed, we should be cautiously cautious,” he said.
“Attractive option”
CoronaVac is one of three experimental COVID-19 vaccines that China has used to inoculate hundreds of thousands of people as part of its emergency program.
The other two vaccines in the Chinese emergency program, both developed by institutions linked to Sinopharm, and another vaccine from CanSino Biologics, have proven safe and triggered immune responses in initial and intermediate trials, according to peer-reviewed articles.
Gang Zeng, a Sinovac researcher involved in the CoronaVac study, said the vaccine could be an attractive option because it can be stored in normal refrigerator temperatures between 2 and 8 degrees Celsius (36 – 46 ° F) and can remain stable. up to three years.
“(It) would offer some benefits for distribution in regions where access to refrigeration is difficult,” Gang said.
Sinovac is conducting advanced-stage large-scale trials of its experimental vaccines in Brazil, Indonesia and Turkey [File: Diego Vara/Reuters]
In contrast, the vaccines developed by Pfizer / BioNTech and Moderna use a new technology called synthetic messenger RNA (mRNA) to activate the immune system against the virus and require much cooler storage.
Pfizer’s vaccine should be stored and transported at -70 ° C although it can be stored in a regular refrigerator for up to five days or up to 15 days in an insulated shipping box. Moderna’s candidate should be stable at normal refrigerator temperatures for 30 days, but for up to six months storage it should be kept at -20 ° C.
CoronaVac is also being studied by Brazil and Indonesia for vaccinations in the coming months.
Indonesia has applied for emergency clearance to start a mass vaccination campaign later this year, and vaccines produced by Sinovac and China’s Sinopharm are expected to be used early in the campaign.
This week, São Paulo’s Brazil will begin importing the first of 46 million doses of China’s Sinovac vaccine against COVID-19 and plans to launch CoronaVac as early as January.
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