Routine administration of the Dengvaxia dengue vaccine in low-transmission areas could increase the number of patients hospitalized with severe secondary infections, according to study data, and led the researchers to recommend patients undergo serological testing before vaccination.
“Successful licensing of the first vaccine against a major global pathogen is a significant achievement,” Neil M. Ferguson, DPhil, director of the MRC Centre for Outbreak Analysis and Modeling, Imperial College London, and colleagues wrote in the journal Science. “However, the dependence of vaccine efficacy on prior immunity presents challenges to planning large-scale use.”
Using mathematical models of dengue transmission, the researchers simulated the effect of routine Dengvaxia (CYD-TDV, Sanofi Pasteur) administration with 80% coverage to examine the result of vaccinating children aged 2 to 18 years, although the vaccine is not approved for use in children aged younger than 9 years.
The researchers reported a modest benefit in high-transmission areas: 20% to 30% reductions in symptomatic disease and hospitalization. In low-transmission areas, however, they reported longer-term (30 years) effects of vaccination on symptomatic disease and hospitalization may be positive or negative, despite mostly positive short-term (10 years) effects.
They also reported a more than 90% reduced risk for hospitalization among seropositive patients who received the vaccine, although they wrote that vaccination put seronegative patients in low-transmission areas at a higher risk for being hospitalized with a secondary infection.
“In places with high transmission intensity, most people have been already exposed to dengue at the time of vaccination, and the vaccine has higher efficacy on average,” researcher Derek A.T. Cummings, PhD, biology professor at the University of Florida, said in a press release. “However, in places with lower transmission intensity, where individuals haven’t been previously exposed, the vaccine can place people at risk of severe disease and overall increase the number of hospitalized cases.”
Ferguson, Cummings and colleagues predicted that routine vaccination would reduce overall incidence of the disease by only 10% to 20%, and wrote that serological testing could help maximize the benefits of the vaccine.
“Our model refines estimates of which places would see a decline in dengue incidence with large-scale vaccination programs, and which places should not implement programs at this point in time,” Ferguson said in the release. “These results present the first published, independent predictions of the potential impact of vaccination that take account of recent data showing that the vaccine can increase the risk of severe dengue disease in young children.” – by Andy Polhamus
Disclosure: The researchers report no relevant financial disclosures.