Experts warn about temporary 'spikes' caused by 'dengue vaccine'

Scientists have warned that dengue vaccines could cause short-term but major spikes in the years after they are first used.

Jan Medlock, an assistant professor at Oregon State University said that their analysis suggested that if they developed and widely used a vaccine for dengue fever, there might later be spikes in the incidence of the disease that were two to three times higher than its normal level.

The research was done by experts at the OSU College of Veterinary Medicine and Clemson University, both of which supported the studies. Scientists used mathematical modeling to examine the quirks of infectious disease transmission that may lead to this quandary. The work was specific to dengue fever, but might also be relevant to other diseases for which vaccines are being sought, such as malaria, and in which the level of protection is less than total.

According to the researchers, the beginning of a vaccination program would slow the numbers of children getting the disease, for a while. But it's expected that a dengue vaccine would not provide total protection against infection. Then, during a period when naturally fluctuating mosquito populations reach an unusually high level, a disproportionate number of children, who were still vulnerable to infection and have never had the disease, would become infected in a short period.

This could cause loss of faith in the vaccination program among the public or policy makers who have never seen such high levels of the disease, stretch the capabilities of health care facilities and workers to care for the sick, and in a worst-case scenario lead people to avoid the vaccine, researchers said. Some short-term spikes could even be as high as seven times the average rate, they said.

A possible way to deal with this phenomenon, scientists said, was literally to vaccinate fewer people. That would cause higher number of people to get the disease in the long run, but reduce the intensity of the spikes and the associated demands on a health care system.

The study is published in Epidemiology and Infection.