An inhalable COVID-19 vaccine developed by China's CanSino Biologics has shown an increase of 250- to 300-fold in neutralising antibody levels as a booster shot, the media reported.

For our comprehensive coverage and latest updates on COVID-19 click here.

According to the latest lab studies by the Chinese drug maker, the aerosolised inhaled adenovirus Type-5 vector-based COVID-19 vaccine (Ad5-nCoV), taken after completing two doses of inactivated vaccine shots for half a year, is proven to be safe and significantly more immunogenic than taking an inactivated vaccine as a booster, the Global Times reported.

In contrast, taking an inactivated vaccine as a booster after two inactivated vaccine shots, increases the neutralising antibodies by only 30 times, it added. The study suggests a heterologous (mix-match vaccine regimen) prime-boost regimen increase the breadth, intensity and duration of the immune response, more than a homogeneous (same vaccine regimen) booster shot, the report said.

CanSinoBIO co-founder and chief scientific officer Zhu Tao cited a previous study conducted in Turkey whose data showed a booster dose of the mRNA vaccine widely used in Western countries for people administered along with two inactivated doses can increase the neutralising antibodies by about 25 times as compared with a booster dose of the inactivated vaccine again.

A similar clinical trial was conducted by US researchers on a heterologous booster shot regimen with three approved vaccines -- one adenovirus-based vaccine by Johnson & Johnson and two mRNA vaccines by Moderna and Pfizer. The results showed that a heterologous regimen enhances immunity.

Homologous boosters increased neutralising antibody titers 4.2- to 20-fold whereas heterologous boosters increased titers 6.2- to 76-fold, said the research report published recently on pre-print server medRvix, meaning it is not yet peer-reviewed. So far, at least 13 provinces and regions in China, such as East China's Anhui and Fujian provinces, and Central China's Hubei Province, have initiated programmes to enhance residents' immunity against COVID-19, the report said.