Mix & Match – CanSino Booster Shot After Second Dose Of Sinovac Covid Vaccine Can Boost Antibodies 78-Fold

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Sep 08 2021
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To speed up its vaccination program in preparation for the possibility of a second wave or the spread of variants of Covid-19, China rolled out its first single-dose vaccine in May. Developed by the Chinese military and Tianjin-based biotech company CanSino Biologics, the homegrown Convidecia vaccine was introduced in at least seven provincial-level regions, including Beijing.


Convidecia was granted a conditional marketing authorization by the National Medical Products Administration of China on 25 Feb, 2021, before getting authorization for emergency use in Hungary in March. The “Ad5-nCoV” vaccine was granted emergency use authorization in Chile, marking the first single-dose Covid-19 vaccine to be approved for emergency use in South America.


In Feb 2021, data released from an interim analysis of Phase III trials with 30,000 participants and 101 Covid cases showed Convidecia had an efficacy of 65.7% at preventing moderate cases of Covid-19 and 90.98% efficacy at preventing severe cases. However, Pakistan trials reported 100% protection from severe disease and 74.8% against any symptomatic Covid-19.

Coronavirus - CanSino Biologics Covid-19 Vaccine

It means the CanSino vaccine has quite a similar efficacy to Johnson & Johnson’s one-dose regimen called “Ad26.COV2.S”, another genetically modified adenovirus vector vaccine with 66% efficacy in a global trial. The vaccine is based on technology similar to the Russian’s Sputnik V and Oxford-AstraZeneca vaccines.


But can we mix and match CanSino with other vaccines? Surprisingly, a booster shot of CanSino Biologics’ vaccine after one or two doses of Sinovac Biotech’s vaccine yields a much stronger antibody response than a Sinovac booster. Yes, it appears three doses of Sinovac are not as effective as mixing CanSino and Sinovac doses together.


Amid concerns over the vaccine’s waning protection over time, which happens to all types of Covid-19 vaccines produced in the world, a study was carried out in China. And they found that participants who received a CanSino booster 3-to-6 months after a second Sinovac shot showed an average 78-fold jump in neutralizing antibody levels some two weeks later.

Coronavirus - China Sinovac Covid-19 Vaccine

In comparison, those who received a Sinovac booster shot (3 doses of the same Sinovac vaccine) showed a 15.2-fold increase in antibody levels. One dose of Sinovac followed by a CanSino booster at an interval of one or two months would increase antibody levels by 25.7-fold, while two doses of Sinovac induced a 6.2-fold increase.


Zhu Fengcai, China’s vaccine clinical trials researcher, said that not only mixing CanSino and Sinovac is safe, the antibody levels would increase and reach its peak (78-fold) at day 14 after the booster shot. He said – “A heterologous prime-boost regimen can increase the breadth, intensity and duration of the immune response, more than a homogeneous boost shot.”


According to the research paper Zhu co-written, there were no thromboses, vaccine-related anaphylaxis, or serious adverse events. The study, based on 300 healthy adults aged 18-59, however, did not test the neutralizing antibody against the more transmissible Delta variant. The exact plan for the booster shots is still under consideration as it still requires regulatory approval.

Coronavirus - China Vaccination - People Getting Covid-19 Injection

The existing vaccination programme says people should be given the same type of vaccine, meaning mixing CanSino and Sinovac vaccines will need more studies. More than 1.4 billion doses of the Sinovac vaccine have been administered globally, about three quarters of them in China. As of Saturday, more than 2.1 billion doses of Covid-19 vaccines had been administered in China.


Zhu’s experimental Recombinant Two-Component Coronavirus Vaccine (ReCOV) against the Coronavirus is undergoing phase I clinical trials in New Zealand and it is expected to enter phase II and III trials in about six weeks. This is the first time a full clinical trials of a Chinese-developed vaccine is to be conducted in a developed country.


On March 16, 2020, Zhu, working with fellow Chinese infectious disease expert Chen Wei, unveiled the world’s first human clinical trials of a Covid-19 vaccine. With various variants spreading around the world, Zhu said it is important to develop a second-generation vaccine against mutated strains.

Coronavirus - Alpha, Beta, Gamma, Delta


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