Brief history of enhanced RSV disease.In 1966, a formalin-inactivated vaccine against RSV (FIRSV) was administered to infants and children in four studies in the United States (26–29). The immunized children were exposed to RSV in the community, and those children who were seronegative for the virus before vaccination experienced a significant increase in the frequency and severity of RSV LRTI. This enhanced form of RSV disease presented with fever, wheezing, and bronchopneumonia and led to frequent hospitalizations (80% in FIRSV recipients versus 5% in controls among RSV-infected children in one study) (26). In fact, two immunized infants died as toddlers as a consequence of subsequent RSV infection (26).

New dengue vaccine performs well in large trial, but safety remains key concern

By Jon CohenNov. 6, 2019 , 5:00 PM
An experimental dengue vaccine has shown promising early results in a large, multicountry trial, but critical questions remain about its effectiveness and safety. Still unclear, for example, is whether the vaccine—which had an efficacy of 80.2% in the study—might increase disease severity in some recipients, as happened with a dengue vaccine given to 1 million children in the Philippines before the problem became clear in 2017.

Critics ‘alarmed by lack of interest’ in studying children put at risk by dengue vaccine

By Jon CohenSep. 4, 2019 , 11:30 AM
Public health experts are debating how to help the 1 million children in the Philippines who received a new vaccine against dengue that could, in rare cases, sicken rather than protect them. The country launched a campaign in 2016 to vaccinate schoolchildren against the mosquito-borne virus, which can cause high fevers, muscle and joint pains, and rashes. One year later, the campaign was suddenly halted after the vaccine’s producer, Paris-based Sanofi Pasteur, announced it could, in rare cases, trigger severe, potentially fatal forms of dengue in children who became infected with the virus despite their vaccination.

Now, critics of the vaccine, named Dengvaxia, say researchers should try to identify those at increased risk of harm, which might save their lives. But Sanofi Pasteur has no plans to conduct a big, complex study, although it is following the fate of about 1% of the vaccinated children for 5 years. “I’m pretty alarmed by the lack of interest,” says retired dengue researcher Scott Halstead, who worked at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, for many years.

Although an epidemic now underway in the Philippines that has sickened nearly 170,000 people likely will have little impact on the frequency of this rare event, it has brought the issue into sharper focus. Halstead calculates that some 500 Filipino children annually could develop severe dengue because of their earlier vaccination with Dengvaxia