China's covid shot triggers immune response but is weaker in over-60s

China’s Sinovac coronavirus vaccine candidate given to 90% of the firm’s employees and their families safely triggers antibodies – but elderly people have a weaker immune response, early trial data suggests

  • China reported positive preliminary results from trials of its coronavirus vaccine on Monday 
  • The vaccine triggered a considerable uptick in coronavirus  antibodies in 90% of trial participants 
  • Its tests in more than 400 adults over 60 found that the shot did not cause significant side effects
  • Elderly participants  in the trial had slightly less robust immune  responses to the vaccine, suggesting it may not provide as strong protection for them

Chinese firm Sinovac Biotech said on Monday its coronavirus vaccine candidate appeared to be safe for older people, according to preliminary results from an early to mid-stage trial, while the immune responses triggered by the vaccine were slightly weaker than younger adults.

Health officials have been concerned about whether experimental vaccines could safely protect the elderly, whose immune systems usually react less robustly to vaccines, against the virus that has led to nearly 890,000 deaths worldwide.

Sinovac’s candidate CoronaVac did not cause severe side effects in a combined Phase 1 and Phase 2 trials launched in May involving 421 participants aged at least 60, Liu Peicheng, Sinovac’s media representative, told Reuters. 

The complete results have not been published and were not made available to Reuters.

It comes as tensions rise between the US and China continue to rise and the vaccine race heats up. Despite the uneasy relationship between the two nations, President Trump has said he would work collaboratively with China to bring a coronavirus vaccine to completion.  

Sinovac researchers told Reuters that the company’s experimental COVID-19 vaccine  triggered  an antibody response in 90% of trial participants – but a weaker one in  over-60s 

Four of the world’s eight vaccines that are in the third phase of trials are from China.

For three groups of participants who respectively took two shots of low, medium and high-dose CoronaVac, over 90 percent of them experienced significant increase in antibody levels. 

While the levels were slightly lower than those seen in younger subjects, this fell in line with expectation, Liu said in a statement. 

Elderly people are among the populations most vulnerable to coronavirus, due to high rates of chronic disease, as well as generally weak immune systems. 

This overall decline in their immune systems also means their immune reactions, including to vaccines, are weaker – a phenomenon referred to as  immunosenescence.  

CoronaVac, being tested in Brazil and Indonesia in the final-stage human trials to evaluate whether it is effective and safe enough to obtain regulatory approvals for mass use, has already been given to tens of thousands of people, including about 90 percent of Sinovac employees and their families, as part of China’s emergency inoculation scheme to protect people facing high infection risk.

The potential vaccine could remain stable for up to three years in storage, Liu said, which might offer Sinovac some advantage in vaccine distribution to regions where cold-chain storage is not an option.

Such estimation is extrapolated from the fact that vaccines readings stayed within acceptable ranges for 42 days at 25 Celsius (77 Fahrenheit), 28 days at 37C (98.6 F), and five months for 2-8C (35.6-46.4 F), Liu said, without disclosing complete data.

(Reporting by Roxanne Liu and Tony Munroe; Editing by Lisa Shumaker)

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