A federal vaccine panel is recommending vaccines for certain children who are traveling to areas where they could be at risk of tick-borne encephalitis or cholera.
The group also discussed flu vaccine effectiveness and a measles, mumps and rubella (MMR) vaccine awaiting licensure.
Recommendations from the Centers for Disease Control and Prevention’s (CDC’s) Advisory Committee on Immunization Practices (ACIP) will not be final until they are approved by the CDC director. They would then be published as official recommendations in Morbidity and Mortality Weekly Report. The AAP will review the CDC’s recommendations and make official policy recommendations of its own.
Tick-borne encephalitis
The ACIP made three recommendations regarding use of Pfizer’s Ticovac vaccine to protect people ages 1 year and older from tick-borne encephalitis.
It recommends the vaccine be given to laboratory workers who may be exposed and to people moving to or traveling to endemic areas who will have extensive exposure to ticks through outdoor activities.
The vaccine also may be considered for people who are moving to or traveling to these areas and might take part in outdoor activities in areas where ticks could be found. This latter group should talk to their doctor about their planned activities, risk factors for severe disease and risk tolerance.
Tick-borne encephalitis is a flavivirus transmitted by Ixodes ticks, usually in or near wooded areas. It is endemic in parts of Europe and Asia, and has the highest risk in April through November. In the past 20 years, there have been 11 cases in U.S. civilian travelers and nine cases in U.S. military members.
While the risk of contracting the illness is low, there is no antiviral treatment. Those who get sick typically are hospitalized and may have permanent physical disabilities or cognitive impairment. About 1% to 20% of cases are fatal.
The Food and Drug Administration (FDA) approved the Ticovac vaccine last year, making it the first such vaccine in the U.S. However, the formulation has been used internationally for more than two decades and has been deemed safe and effective.
The vaccine is given in a three-dose primary series with the dose timing dependent on the age of the recipient. ACIP members approved use of the vaccine with a 15-0 vote.
“Clinicians practicing travel medicine will hopefully really enjoy the flexibility and thoughtfulness that went into this recommendation,” said ACIP member Camille N. Kotton, M.D., FIDSA, FAST, clinical director, transplant and immunocompromised host infectious diseases at Massachusetts General Hospital.
Wilbur H. Chen, M.D., M.S., FACP, FIDSA, professor of medicine at the University of Maryland School of Medicine, noted that while infection is very rare in travelers, global warming is impacting tick and mosquito habitats and the circulation of flaviviruses.
“This is just a reminder that flaviviruses, among which (are) dengue, West Nile, yellow fever, continue to scorch the world, and so I think that we will see these types of vaccines becoming more and more important,” he said.
Cholera
ACIP also voted 14-0 with one abstention to recommend the Vaxchora cholera vaccine for children and adolescents ages 2-17 years who are traveling to an area with active cholera transmission. The group already recommends the vaccine for adults ages 18-64 years.
There are 15 countries in Africa and Asia that have active transmission of cholera, a bacterial disease that spreads in areas with poor sanitation and limited access to safe drinking water.
Vaxchora, from Emergent Travel Health, is a single dose, live, attenuated oral vaccine that can reduce severe diarrhea by 90% 10 days after vaccination, according to the CDC. Production was temporarily discontinued during the pandemic, but it is expected to resume in May.
The vaccine is more complicated to administer than others as it involves a buffer solution with strict rules. The manufacturer is planning to ask the FDA in the coming months to allow it to be mixed with a sweetener.
There is no data on administration of the vaccine to pregnant or immunocompromised travelers, but these groups should talk to their doctor about the risks related to traveling to areas with active cholera transmission. ACIP typically does not recommend giving live vaccines to people who are immunocompromised.
MMR
GlaxoSmithKline (GSK) presented phase 3 clinical trial data on its MMR vaccine, Priorix, saying it is just as safe and effective as Merck’s M-M-R II vaccine. It has proposed using Priorix in children ages 12 months and older as a two-dose series. GSK also hopes to get approval for use as the second dose in people who first received M-M-R II.
Priorix is awaiting FDA approval. If it comes in the next few months, ACIP could vote on use of the vaccine at its June meeting.
Influenza
Early interim data show flu vaccine effectiveness is low this season — about 8% against any influenza A strains and 14% against H3N2, which has been the most common virus type this season. However, the CDC cautioned the data are limited by a small flu positivity rate at sites in the study and noted health care seeking behavior during the pandemic may affect the estimates. It was not able to break down the estimates by age group or vaccine brand and the effectiveness estimates are only for prevention of mild illness, not hospitalization.
Outpatient visits for flu-like illness have been below baseline for the last several weeks but flu continues to circulate sporadically, according to the CDC. Hospitalization rates are higher than last season but lower than the four seasons prior to the COVID-19 pandemic. Five children have died of flu this season.
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