COVID-19 vaccine volunteers get second dose to determine validity

vaccine Photo:VCG

China‘s earliest COVID-19 vaccine volunteers were offered a second dose on Sunday to strengthen their immunity after getting their first one in March. Volunteers will start a new one-year observation after the injection and their blood samples will be collected at least five times to measure their antibody levels.

Part of China‘s first group of 108 volunteers started to get their second low-level dose of the domestic-made Recombinant Novel Coronavirus Vaccine (Ad5-nCoV) on a voluntary basis on Sunday, after they concluded their six-month follow-up period for the Phase I clinical trials, which began on March 17 in Wuhan, capital of Central China‘s Hubei Province. The vaccine is co-developed by Tianjin-based biotechnology company CanSino Biologics Inc and military infectious diseases expert Chen Wei.

“We were offered a free extra dose of the Ad5-nCoV vaccine to intensify our immune response against the virus, and as far as I know, at least 80 volunteers signed up,” Zhu Aobing, 28, one of the volunteers, told the Global Times on Sunday.

The purpose of the second dose, for researchers, is to further observe the safety and immunogenicity of the vaccine, a Beijing-based immunologist who asked to be anonymous, told the Global Times on Sunday.

Volunteers do not have to be quarantined for intensive observation after the second inoculation, but they have to provide blood samples at least five times within one year, Zhu noted. He said he did not experience any adverse reaction after the second dose, and had no local pain, redness or swelling at the injection site.

Similar to the Phase I trial, the volunteers will undergo medical observation six times – on the day after the second injection, the next day, day 14, day 28, six months and 12 months. 

It‘s only been a bit more than half a year since the COVID-19 outbreak, but there still lacks enough data to say for sure how long a vaccine will be effective, Chen suggested in a previous interview with the Xinhua News Agency. But the current data from first two phases‘ clinical trials of Ad5-nCoV show that the first dose taken in March is still effective.

Further study is being undertaken to explore how long the protection can last, Chen said. Taking Ebola vaccine as a reference, the effects recede in the sixth month after the first dose, but a prompt extra dose in the sixth month can rejuvenate the immune response and extend the effectiveness to two years, Chen said.

The Ministry of Industry and Information Technology on Sunday announced plans to establish a special group to ensure the production of COVID-19 vaccines, to prepare for and guide the large-scale production of vaccines.


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