麻豆传媒

Laboratory workers and travelers to endemic countries with risk of exposure should be vaccinated against tick-borne encephalitis (TBE), and children traveling to areas with active cholera transmission should receive the cholera vaccine, the CDC Advisory Committee on Immunization Practices (ACIP) said Wednesday.

In a unanimous 15-0 vote, the ACIP recommended the TBE vaccine for laboratory workers with potential risk of exposure to TBE virus, and a 15-0 vote recommended the vaccine for people traveling to a TBE-endemic area who will have extensive exposure to ticks "based on their planned outdoor activities and itinerary."

A third 15-0 vote found that vaccination may also be considered for those traveling or moving to a TBE-endemic area, who "might" engage in outdoor activities in areas with ticks, based on shared clinical decision-making, with "an assessment of their planned activities and itinerary, risk factors for a poorer medical outcome, and personal perception and tolerance of risk."

FDA approved the TBE vaccine (Ticovac) in August 2021 for individuals, ages 1 year and up, traveling to or living in TBE-endemic areas. The vaccine has been approved abroad since 1976.

Susan Hills, MBBS, of the CDC, classified TBE cases as "very rare," with less than one TBE case per 30 million trips to TBE-endemic countries. Even if travelers are visiting during the TBE transmission season (April to November) and participating in outdoor activities with high risk of tick exposure, the rate is still about one TBE case per 2 million trips.

While only 11 cases of TBE occurred among U.S. travelers from 2001-2020, Hills noted that the virus has "potentially high fatality and sequelae rates with neuroinvasive disease." Most people infected require hospitalization, and there is no antiviral treatment. Sequelae can include permanent physical disabilities or cognitive impairment, and the case fatality rates range from 1% to 20%, Hills added.

Cases of aerosol transmission have occurred in laboratory settings, with more than 46 laboratory-acquired infections globally, Hills said. Given that more than 10 U.S. laboratories work with TBE virus, vaccination can reduce the risk of severe disease.

The conditional recommendation for travelers with low risk of exposure arose from the fact that there were no specific risk factors for TBE infection, with no apparent association with duration of travel, specific activities, demographics, or travel locations in eight TBE cases with itinerary information available. All were exposed to ticks and traveled during the TBE virus transmission season, Hills said.

There was little debate about these recommendations, with only a suggestion about more extensive qualifications to recommend the TBE vaccine, but CDC staff assured ACIP members that there would be more specific information in the clinical considerations.

Cholera Vaccine

ACIP also voted 14-1-0 (there was an abstention due to conflict of interest) to recommend the oral live attenuated cholera vaccine, lyophilized CVD 103-HgR (Vaxchora), for children and adolescents, ages 2-17 years, traveling to an area with active cholera transmission.

FDA approved the vaccine for adults in 2016, and it received a in December 2020. While production was temporarily suspended during the pandemic, the vaccine will be available beginning May 1, 2022.

ACIP members raised few concerns with the vaccine, except the potential for transmission to immunocompromised family members, given this is a live vaccine. However, Jennifer Collins, MD, of the CDC, pointed to a phase I trial that showed no household transmission of the vaccine. Among 24 household contacts of 66 healthy adults, none had vaccine strain isolated from stool on day 7 or on day 28.

As always, ACIP recommendations are not considered final until they are published in the Morbidity and Mortality Weekly Report.

Comment