Vietnam develops next-generation Japanese encephalitis vaccine

Experts discussed the results of studies on Vietnam’s second-generation Japanese encephalitis vaccine, developed using Vero cell technology, at the conference on preventive medicine.

The vaccine has been evaluated for safety, immunogenicity and optimal dosage in healthy children aged 9 to 24 months.

Developed and manufactured by Company for Vaccines and Biological Production No.1 under the Ministry of Health, the vaccine was reported to be well tolerated and to have elicited a strong immune response among participating children.

The research team is currently completing the documentation required for marketing authorization.

According to information published on the company’s official website, the registration dossier is expected to be completed in 2026.

Named JECEVAX, the vaccine is available in multidose and single-dose formulations.

It is an inactivated vaccine manufactured using Vero cells and the Beijing-1 virus strain, representing an advancement in vaccine production technology in Vietnam.

How does the new vaccine differ from earlier versions?

According to a technical document reviewed and approved by the Vietnam Association of Preventive Medicine, the main differences between older and newer generations of Japanese encephalitis vaccines lie in their manufacturing technologies, ability to induce an immune response and duration of protection.

Older vaccines include inactivated vaccines produced from mouse brain tissue and those manufactured using Vero cell cultures.

The newer-generation vaccine discussed in the document, by contrast, is a live attenuated recombinant chimeric vaccine, which is also produced using Vero cells.

Research in Vietnam has shown that immunity from the older mouse brain-derived inactivated vaccine can decline over time.

After three doses, the proportion of children with protective antibody levels fell from 80 percent after one year to 76 percent after four years and 52 percent after seven years, indicating the need for booster doses to maintain protection.

For the inactivated vaccine produced using Vero cells, the document reports that the proportion of recipients with protective antibody levels declined from 83 percent six months after the primary two-dose series to 58 percent at 12 months and 48 percent at 24 months.

By comparison, clinical studies of newer-generation vaccines have demonstrated the potential to produce a rapid immune response with a single primary dose.

One study found that 99.3 percent of children achieved protective antibody levels 28 days after vaccination, while another reported that 85 percent of children maintained protective antibody levels five years later.

Japanese encephalitis is an acute infectious disease that can cause severe damage to the central nervous system, leaving survivors with lasting motor impairments and other neurological complications, according to experts.

The disease also carries a substantial risk of death and primarily affects children under 15.

Vietnam began producing Japanese encephalitis vaccines in 1992 and incorporated the vaccine into its expanded program on immunization in 1997.

The development of JECEVAX represents a further step in the country’s efforts to strengthen domestic vaccine research and manufacturing capabilities.