An experimental vaccine to prevent the mosquito-borne illness chikungunya proved to elicit antibodies in all 25 adult volunteers who received it.
Chikungunya is characterized by sever joint pain accompanied by headache and fever, the National Institute of Health reported. As of right now there are no vaccines available to prevent or treat the infection.
The infection was first identified in East Africa in the early 1950s, since then there have been large outbreaks in Thailand and India; it did not reach the Western Hemisphere until 2013. As of August 8 there were over 570,000 confirmed or suspected cases throughout the Americas. There have been 484 cases reported in the Unites States as of August 5; the first two locally acquired cases were reported in Florida in mid-July.
"The two species of mosquito that spread chikungunya virus are found in parts of the continental United States, so it may just be a matter of time before this illness gains a foothold here," said NIAID Director Anthony S. Fauci, M.D. "Therefore, it is prudent to begin addressing this emerging public health threat with the development of vaccines, such as this one, which was designed and tested by scientists from the NIAID Vaccine Research Center."
In 2010 the Vaccine Research Center (VRC) tested the candidate chikungunya vaccine in non-human primates; all of the study subjects were protected from the virus when later exposed.
In this new trial, 23 healthy volunteers were given three injections at different doses over a 20-week period. Antibody levels were measured several times over the course of the trial following each injection. The team detected chikungunya neutralizing antibodies in all volunteers after the second injection, even those who received the lowest doses; a significant boost of these antibodies was detected following the third injection. The antibodies appeared to persist for 11 months, suggesting the vaccine could effectively protect against the infection.
"The candidate vaccine prompted a robust immunological response in recipients and was very well tolerated," said VRC scientist Julie E. Ledgerwood, D.O., principal investigator of the trial. "Notably, the levels of neutralizing antibody produced in response to the experimental vaccine were comparable to those seen in two patients who had recovered from a chikungunya virus infection acquired elsewhere. This observation gives us additional confidence that this vaccine would provide as much protection as natural infection."
