A new study has found that the experimental dengue vaccine being developed by French pharmaceutical brand, Sanofi, may yield varying effects to different age groups. More specifically, younger children are more likely to still get hospitalized due to the infection compared to older children in the study group.

The researchers investigated the live, attenuated and tetravalent dengue vaccine called CYD-TDV in three clinical trials by testing its efficacy in more than 35,000 children aged 2-14 years and 9-16 years in select Asia-Pacific and Latin American countries respectively. After the initial dose, the vaccine was administered for two more times, particularly during the 6th and 12th month. Follow-up surveillance was then performed after 25 months or 13 months after the third dose to determine the efficacy of the vaccine in combating dengue cases with established virology. Safety of the participants was also determined during the said follow-up study.

The findings of the study, published in the New England Journal of Medicine, showed that 80.8 percent of the study group aged 9 years old and above are likely to prevent hospital confinement due to dengue. Meanwhile, children aged 2-5 years old, or when they were struck by natural infection in the third year of immunization, are at an increased risk of hospitalization.

The exact reason why the study was able to come up with such notable findings is not clearly established, writes Cameron Simmons in an editorial accompanying the journal study post. According to him, the results of the research may be due to chance; however, the possibility that some children were not hospitalized even though they feel ill may also be considered. He stressed that the study only focused on hospitalization rates so some cases of dengue, which did not resort to hospital admission, may have been missed. Simmons is a researcher from the University of Oxford specializing in dengue, and is not part of the study.

The researchers also delved into the immunogenicity and reactogenicity among a subgroup from the study subjects. They found that immunization can indeed decrease the occurrence of dengue cases that are virologically established and exhibit favorable reactogenicity and safety levels - all of which were consistent with previous results.

With the data collated for this study, the researchers concluded that the participants who received the vaccine during the efficacy surveillance stage exhibited a decrease in the diagnosis of dengue. This finding is true among children in Asia-Pacific and Latin-American tropical and subtropical locations. The research group acknowledged that children aged 9 years old and above showed a lower risk of contracting dengue two years after the administration of the third dose of vaccine compared to children aged eight years and below.

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