As warmer temperatures herald annoying mosquitoes, the researchers are feverishly working on several promising vaccines against zika, a virus known to infect humans through the bite of this insect. The speed and debilitating effects of last year's zika outbreak in the Western Hemisphere generated a race to develop a vaccine. Just over a year after this pandemic was declared a global health emergency, a group of volunteers are undergoing preliminary testing.
Researchers say that uncertainty over whether the zika epidemic will continue will affect its ability to complete testing. They need areas with an active viral outbreak to perform large-scale human trials, and make sure the vaccine actually protects against the disease.
"On the one hand, you do not want to see outbreaks of infection," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID). But on the other hand [without them], you may have to wait a long time to make sure the vaccine works. "
All of the vaccines being tested are now under Phase I clinical trials, meaning that safety testing is being done on a small number of people. According to a review article published on Tuesday 21 February in Immunity magazine, vaccines represent a variety of scientific techniques to thwart the disease, ranging from inactivation of the virus to the manipulation of its DNA (Genetic material).
NIAID announced Tuesday that it is launching another Phase I trial for a vaccine made based on proteins found in mosquito saliva. This vaccine seeks to trigger a response of the human immune system to the saliva of the mosquito and any virus that is in the saliva. If successful, the product could protect people against a spectrum of mosquito-borne diseases, including zika virus.
Colonel Nelson Michael, director of the US Military HIV Research Program at the Walter Reed Army Institute of Research and co-author of the article, said he expects preliminary reports in April about the safety of some of the vaccines that began to be investigated First. From now on, he said, it is impossible to guess which vaccine will prove to be most effective in generating immunity.
"Sometimes it's hard to predict which horse will win the race," Michael said.
Zika, which is transmitted from person to person by mosquito bites or sexual contact, often infects without presenting symptoms. In some cases, it causes some similar to flu, such as fever, muscle aches and joint pain in adults and, rarely, Guillain-Barré syndrome, which can cause temporary paralysis. But the virus is most notorious for causing some children whose mothers were exposed to zika to be born with microcephaly: a birth defect whereby the baby's head is smaller than the average size, which causes severe developmental delays.
The virus attracted international attention after the appearance of hundreds of cases of babies with microcephaly in Brazil. It quickly crossed South America and the Caribbean before stopping on the southern coast of the United States.
The World Health Organization declared the outbreak a "public health emergency of international concern" On February 1, 2016, and then ended the alert on November 18.
Vaccines that meet the safety standard in phase I clinical trials are subjected to subsequent rounds of testing to measure effectiveness. To know the effectiveness, researchers rely on the gold standard of administering the vaccine to a large number of people at risk to see if the drug is effective. However, the arrival of zika in the Western Hemisphere is recent, meaning researchers do not know if the virus will become a constant threat, or if it was only a single explosion.
Uncertainty raises several implications for accelerating the development of a vaccine. A pause in the outbreak could cause significant delays in testing, which would also delay the appearance of a commercially available product, Fauci said.
While researchers may use alternative methods to measure efficacy without large-scale testing, a decrease in virus circulation could delay the process for years because vaccine testing would not be effective.
"If we do not have many infections this season in South America and Puerto Rico, it may take years to make sure the vaccine works," he said.
Fauci expects to launch the next round of human trials for a DNA vaccine developed by NIAID in March.
Michael also worries that the decline in the number of cases could lead the private sector to withdraw funds for the development of the vaccine. It takes millions of dollars to develop a drug or vaccine, and pharmaceutical companies play a critical role, he said. But these companies have many competitive interests, he added, and if it is difficult to test a vaccine this year, zika's prevention efforts, both public and private, can be diverted to other areas.
"This is a constant problem, where they put their resources", he said.
So far, the signals suggest that the weather could again be conducive to zika this year. Temperatures, warmer than usual, are affecting areas throughout the Western Hemisphere, CBS reported, including outbreak outbreaks in Brazil. Higher temperatures increase the voracity of the main transmitter of the zika virus, the Aedes aegypti mosquito.
In the United States, areas with populations of Aedes aegypti are closely monitoring the number of mosquitoes. Last year, Texas and Florida dealt with local cases of zika infection (not transmitted by travelers).
According to the Centers for Disease Control and Prevention (CDC), 1,073 cases of zika were found in laboratory tests (up to February 22, 2017). Florida has an information line on zika, coordinated by the Department of Health: 1-855-622-6735.
In Texas, public health officials have monitored mosquito populations throughout the winter to track their numbers and the presence of the virus. Chris Van Deusen, a spokesman for the Texas Department of State Health Services, has seen fewer Aedes aegypti numbers and no cases of zika virus.
Van Deusen said the state is also monitoring the outbreak in Mexico, as heavy cross-border traffic increases the likelihood of transmission. Officials also expect another outbreak of local transmission cases, he said.
"There are so many factors to take into account that it is impossible to make a solid prediction," he said.
This story was produced by Kaiser Health News, an editorially independent program of the Kaiser Family Foundation