A new vaccine in its first human trials may offer protection against the chikungunya virus, a mosquito-borne infection that causes fever and severe joint pain, researchers reported Thursday in The Lancet.

As of June 13, there were an estimated 166,000 suspected cases in the Caribbean and South America. Last month, the first cases in the United States were reported in Florida.

The first phase of the trial — to test for safety and immune response — involved 25 participants and found no serious side effects. All participants developed antibodies that lasted at least six months after the last of three injections, suggesting the vaccine might provide long-term protection.

“The exciting finding in this trial is both the fact the vaccine was so well tolerated and we measured impressive antibody levels in the recipients” that were similar to levels in people who had recently recovered from chikungunya, said Dr. Julie E. Ledgerwood, the senior author of the study and chief of the clinical trials program at the Vaccine Research Center, part of the National Institutes of Health. That similarity is important, she said, because “people who make a robust response after recovering appear to be protected from future infections.”