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BEIJING, Oct. 24 (Xinhua) -- At least 46 COVID-19 vaccines are being tested in human trials in China and more than 20 in overseas clinical trials as the country pushes forward its vaccine research and development through multiple tech routes.

Among them, three inactivated monovalent vaccines designed to neutralize Omicron variants are in testing for sequential immunization in the Chinese mainland, Hong Kong and the United Arab Emirates, and these tests are going well.

In addition, two domestically-developed mRNA-based COVID-19 vaccine candidates have proven effective in preclinical trials, showing their potential for human tests, according to a June paper published in the journal Emerging Microbes &Infections.

The study has shown that the two vaccines, the mRNA-Beta and mRNA-Omicron, can induce high-titer neutralizing antibody levels against original and multiple SARS-CoV-2 variants, such as Beta, Delta and Omicron.

Also, a China-developed recombinant protein vaccine against COVID-19 has shown to be safe and effective in late-stage human trials, according to a study published in May in The New England Journal of Medicine.

This vaccine had an efficacy against COVID-19 of any severity of 81.4 percent in the short-term follow-up and 75.7 percent in the long-term follow-up.

Nine Chinese multivalent vaccines against COVID-19 variants have been put into clinical trial, with some of them entering into the third phrase, the last stage before approval for marketing.

In addition, a Chinese group proposed a quadrivalent mosaic nanoparticle candidate COVID-19 vaccine comprising spike proteins from the SARS-CoV-2 prototype, and Alpha, Beta, and Gamma variants.

The study published in May in the journal Nature Communications revealed that this nanoparticle candidate vaccine had elicited equivalent or superior neutralizing antibodies against variant strains in mice and non-human primates with only a small reduction in neutralization titers against the ancestral strain.

The development of broad-spectrum vaccines is also in the pipeline in China, according to the research group under the State Council joint prevention and control mechanism against COVID-19 and other relevant research teams.

The country is developing COVID-19 vaccines targeting easier drug-delivery as well.

An aerosolized adenovirus type-5 vector-based COVID-19 vaccine (Ad5-nCoV) administered via oral inhalation has been approved for emergency use among populations who have been inoculated with two doses of inactivated vaccines for six months.

Its inhalable dosage is only one-fifth that of intramuscular injection and the clinical trial proved it safe and effective in adults as a booster jab.

Until now, nine COVID-19 vaccines developed with different tech routes have gotten conditional market approval or been greenlighted for emergency use in China. Three of them have been included on the World Health Organization list of vaccines for emergency use.

(Web editor: Cai Hairuo, Du Mingming)