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Sinovac Biotech’s experimental COVID-19 vaccine, CoronaVac, triggered a rapid immune response, but the level of antibodies produced was lower than in people who had recovered from the disease, trial results showed on Wednesday.
Although early-to-mid-stage trials were not designed to assess the effectiveness of CoronaVac, the researchers said it could provide sufficient protection, based on their experience with other vaccines and data. preclinical studies on macaques.
The study follows encouraging announcements this month from U.S. drug makers Pfizer and Moderna, as well as Sputnik V in Russia, that their investigational vaccines were over 90% effective based on interim data from ‘large-scale trials in the final phase.
CoronaVac and four other investigational vaccines developed in China are currently in late trials 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, come from the results of phase I and phase 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 vaccination 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. from Jiangsu to Nanjing and one of the authors of the article.
CoronaVac is one of three experimental COVID-19 vaccines that China is using to inoculate hundreds of thousands of people as part of its emergency use program [File: Thomas Peter/Reuters]
“We believe this makes the vaccine suitable for emergency use during the pandemic,” Zhu said in a statement released alongside the document.
Among the limitations of the phase II trials, 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 60 years of age or older, or with other underlying illnesses.
It also did not assess the responses of T cells, which they say will be part of phase III trials in Brazil. Phase III trials are also underway in Indonesia and Brazil, which have reported the most 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, 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 released.
“But even then, after the phase III trial is over and after approval, we have to be careful,” he said.
‘Attractive option’
CoronaVac is one of three experimental COVID-19 vaccines that China is using to inoculate hundreds of thousands of people as part of its emergency use program.
China’s two other emergency program vaccines, both developed by institutes linked to Sinopharm, and another vaccine from CanSino Biologics, have also been shown to be safe and trigger immune responses in early and intermediate trials, according to articles. peer reviewed.
Gang Zeng, a Sinovac researcher involved in the CoronaVac study, said the vaccine could be an attractive option because it can be stored at normal refrigerator temperatures between 2 and 8 degrees Celsius (36 ° – 46 ° F) and can remain stable for up to three years.
“(This) would provide some benefits for distribution in areas where access to refrigeration is difficult,” Gang said.
Sinovac conducts large-scale trials of its advanced investigational vaccines in Brazil, Indonesia and Turkey [File: Diego Vara/Reuters]
In contrast, 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 vaccine should be stored and transported at -70 ° C although it can be stored in a normal refrigerator for up to five days, or up to 15 days in a thermal shipping box. Moderna’s candidate should be stable at normal refrigerator temperatures for 30 days, but for storage up to six months it should be stored at -20 ° C.
CoronaVac is also being considered by Brazil and Indonesia for inoculations in the coming months.
Indonesia has requested emergency clearance to launch a mass vaccination campaign by the end of the year, and vaccines produced by China’s Sinovac and Sinopharm are expected to be used in the early stages of the campaign.
The Brazilian Sao Paulo is expected to start importing the first of 46 million doses of China’s Sinovac vaccine against COVID-19 this week and plans to deploy CoronaVac as early as January.
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