CanSino's inhaled Covid-19 vaccine booster induces a higher level of immune response for those vaccinated with two Sinovac shots than a third dose of the Sinovac vaccine, a team of Chinese researchers has found.
Study participants who received the CanSino booster showed "much stronger neutralising antibody responses" - at nearly seven to 11 times higher than that of a three-dose regimen of the Sinovac shot - according to the study of 420 people. The study has not been peer-reviewed.
The results indicated "a potential boost strategy" for people primed with inactivated Covid-19 vaccines, said the team, which included scientists from the Jiangsu provincial centre for disease control and prevention, the Chinese military's top epidemiologist and virologist Chen Wei and CanSino Biologics employees.
They posted the results on the platform Preprints with The Lancet last week.
Tianjin-based CanSino said the needle free, non-invasive treatment aimed to provide quick, regular and mass-scale protection with easy administration.
China's mass vaccination campaign has relied heavily on domestically developed inactivated shots from Sinopharm and Sinovac, both approved for emergency use by the World Health Organisation and widely used by developing countries.
Beijing has yet to approve heterologous vaccination, or administering a different vaccine to the original regimen.
If approved, the CanSino Covid-19 vaccine is the most likely product to be used because it is the only non-inactivated Covid-19 vaccine approved for general launch in the country, a prerequisite for mixing and matching vaccines.
But the product will need to go through clinical trials for approval. A late-stage human trial involving 13,000 participants was registered on the ClinicalTrials.gov database last month.
The company has not estimated its annual product capacity, however it expects the smaller amount required for inhaled doses than the same dose via injection to allow its product to go further.
The WHO has suggested that countries using inactivated shots approved by the agency for the first dose then use mRNA or vectored vaccines as part of a two-dose regimen or as a booster for better protection.
Inactivated jabs use dead material from the virus to trigger the immune system, while CanSino’s vaccine uses an adenoviral vector to deliver a virus antigen and trigger an immune response.
Injected vaccines induce system immune responses that do not specifically target the pathogen’s region of infection. But inhaled vaccines imitate natural infection by the virus and target mucosal surfaces – the nose, throat and lungs, the point of entry for pathogens – to induce a localised immune response.
The Chinese team found fewer cases of adverse reactions in the inhaled booster groups, which reported reactions such as fatigue, headache and fever. Some people said they had a dry mouth and their throat swelled.
The study showed that the inhaled booster had a high neutralising capability against the Delta variant – about three times the WHO international standard – while a Sinovac booster was 20 per cent lower than the benchmark.
When compared to a third dose of Sinovac, the CanSino booster showed 18-24 times higher cross-neutralising capability against Delta 28 days after the booster, according to the study.
This article was first published in South China Morning Post.