Chinese Covid vaccine safe, generates immune response, trial results published in Lancet say

The most common adverse reaction to CoronaVac has been reported as injection-site pain. The occurrence of fever after vaccination has also been found to be relatively low.

Representational image | A worker checks syringes of CoronaVac on the production line at Sinovac Biotech in Beijing | Photo: Kevin Frayer | Getty Images via Bloomberg

New Delhi: Results of the phase 1/2 clinical trials of a Chinese Covid-19 vaccine have shown it to be safe and generate a good antibody response.

CoronaVac, manufactured by Sinovac Life Sciences in Beijing, contains an inactivated SARS-CoV2 virus. The results of the trial have been published in The Lancet Infectious Diseases journal.

“We found that two doses of CoronaVac at different concentrations and using different dosing schedules were well tolerated and moderately immunogenic in healthy adults aged 18–59 years. The incidence of adverse reactions in the 3 μg and 6 μg group were similar, indicating no dose related safety concerns but more long-term follow-up is needed,” the researchers said.

They also noted that “most adverse reactions were mild, with the most common symptom being injection-site pain, which is in accordance with previous findings for another inactivated Covid-19 vaccine from Sinopharm (another Beijing-based pharmaceutical group)”.

Compared with other Covid-19 vaccine candidates such as viral-vectored vaccines or DNA or RNA vaccines, the researchers noted, the occurrence of fever after vaccination with CoronaVac was relatively low. Only one case of acute hypersensitivity, with manifestation of urticaria 48 hours after the first dose of study drug was reported in one group.

Since this was an early stage trial vaccine candidate, its efficacy was not being tested.

As many as 144 participants were enrolled in the phase 1 trial of the vaccine candidate between 16 and 25 April. And 600 participants were enrolled in its phase 2 trial between 3 and 5 May. A total of 743 participants had received at least one dose of the vaccine.

Vaccine generated neutralising antibodies

The mean neutralising antibody titres (indicating the level of antibodies in a blood sample) induced by CoronaVac ranged from 23.8 to 65.4, which were lower than levels seen in people who have previously had Covid-19 (average level of 163.7).

However, the researchers still believe that CoronaVac could provide sufficient protection against Covid-19 based on their experience with other vaccines and data from preclinical studies with macaques.

Dr Gang Zeng, one of the authors of the study, from Sinovac Biotech said, “CoronaVac is one of many Covid-19 vaccine candidates that are being explored in parallel. There are a multitude of different vaccine technologies under investigation, each with their own advantages and disadvantages. CoronaVac could be an attractive option because it can be stored in a standard refrigerator between 2 and 8 degrees centigrade, which is typical for many existing vaccines, including flu.”

Zeng added, “The vaccine may also remain stable for up to three years in storage, which would offer some advantages for distribution to regions where access to refrigeration is challenging. However, data from phase 3 studies will be crucial before any recommendations about the potential uses of CoronaVac can be made.”