Dengue Vaccine Only Effective In Some Children

The recombinant, live-attenuated, tetravalent dengue vaccine (CYD-TDV) is highly effective for all dengue serotypes in children older than age 5 years with immunity from prior exposure to dengue virus, according to a recent study. However, the vaccine is significantly less effective in children with no prior exposure.

To explore the effect of age and immunity status on vaccine efficacy, the researchers combined data from the CYD14 and CYD15 trials and estimated the vaccine efficacy for each of the 4 dengue virus serotypes and for all serotypes combined.
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Participants were categorized by age and baseline immunity status. Results were adjusted for uncertainty of baseline immunity status in some participants.

Results indicated that the vaccine was highly effective against all serotypes in participants who were seropositive at baseline (70.2% for serotype 1, 67.9% for serotype 2, 77.5% for serotype 3, 89.9% for serotype 4, and 75.4% overall). However, in seronegative participants, the vaccine was only moderately effective against serotype 4, but not against other serotypes.

Additionally, the researchers found that overall vaccine efficacy tended to increase with age (35.9% for children aged 5 years or older, 65.6% for age 6 to 8 years, 73.4% for age 9 to 11 years, and 80.6% for age 12 or older).

“The CYD-TDV vaccine was highly efficacious for all dengue serotypes among children aged [older than 5 years] who have acquired baseline immunity from previous exposure,” the researchers concluded. “Increasing vaccine efficacy with age was not fully explained by increasing prevalence of baseline immunity with age.”

—Christina Vogt

Reference:

Yang Y, Meng Y, Halloran ME, Longini Jr IM. Dependency of vaccine efficacy on preexposure and age: a closer look at a tetravalent dengue vaccine. Clin Infect Dis. 2018;66(2):178-184. https://doi.org/10.1093/cid/cix766.