At nearly 117,000 pre-travel health consultations over 10 years at 31 US sites, 68% of eligible travelers weren't offered the pneumococcal vaccine and 15% weren't offered the flu vaccine—even if their destination was experiencing its flu season, Harvard Medical School researchers and their colleagues reported yesterday in Open Forum Infectious Diseases.
The team analyzed online questionnaires completed by Global Travel Epidemiology Network patients and providers at pre-travel health consultations and developed multivariable logistic regression models to identify characteristics tied to receiving the vaccinations from July 2012 through June 2022.
Pre-travel health consultations focus on counseling and ensuring that travelers are up to date on routine vaccinations. The average age of the travelers evaluated was 38 years, 57% were female, and the most common destination was Africa (42%). Most (59%) planned to travel for at least 2 weeks.
"Infections by Streptococcus pneumoniae and influenza viruses are vaccine-preventable diseases causing great morbidity and mortality," the researchers wrote. "Influenza is a top travel-related risk, with an estimated incidence of at 1% per month of travel."
Barriers to vaccination
At the 116,865 pre-travel visits, 25% of travelers were eligible to receive the pneumococcal vaccine, but only 68% of the eligible patients were offered vaccination. The most common reason cited for not offering the pneumococcal vaccine was that the provider didn't think it was indicated for the traveler's itinerary.
Notably, influenza vaccines expire June 30th of each year and are generally not available in the United States between July and late August.
"While the pneumococcal vaccine is not a travel-related vaccine per se, these travel clinic visits represent missed opportunities for vaccination, either during the visit or through referral to another provider," the researchers wrote.
Barriers to pneumococcal vaccination may include a lack of insurance coverage for non-travel vaccines at a pre-travel health consultation or a lack of vaccine stock at some travel clinics, they said.
Of the 48% of travelers eligible for the flu vaccine, 15% weren't offered it, and another 30% declined it. For 14% of eligible travelers, flu vaccine was unavailable. In addition to vaccine refusal, other barriers were a lack of vaccine availability (20%) and the provider not considering the vaccine indicated for the itinerary (19%).
"These two barriers were most common during travel visits that occurred between April and September," the study authors noted. "Notably, influenza vaccines expire June 30th of each year and are generally not available in the United States between July and late August."
Travelers were less likely to be vaccinated if they were seen at clinical sites outside the Northeast (Midwest odds ratio [OR], 0.32; South OR, 0.53; West OR, 0.33) or if they visited non-academic centers (OR, 0.52). Also, travelers aged 65 years and older were more likely to be vaccinated (OR, 6.07), as were those with one or more underlying medical conditions (OR, 1.61).
Raising awareness of global flu epidemiology, seasonality
Of the 56,150 travelers eligible for the flu vaccine, 59% were traveling to a destination during its flu season.
Including the destination-specific risk of influenza in resources frequently consulted by providers and travelers, such as the CDC Traveler's Health website, may be another way to raise awareness.
"Increasing awareness of global influenza transmission patterns and improving access to routine vaccines at the pre-travel encounter may enhance vaccination for respiratory pathogens in departing U.S. international travelers," the study authors wrote. "Furthermore, there are multiple destinations, most notably Kenya, Malaysia, and Singapore, among other tropical climates, in which influenza transmission is year-round."
They recommended encouraging providers to use resources on the global epidemiology and seasonality of flu such as those from the World Health Organization. "Including the destination-specific risk of influenza in resources frequently consulted by providers and travelers, such as the CDC Traveler's Health website, may be another way to raise awareness," they wrote.
Making a Northern Hemisphere flu vaccine available to travel clinics during the US summer could also be useful. "One possible approach would be to permit travel clinics to utilize influenza vaccines beyond the June 30th expiration date for eligible travelers whose itinerary involves an area with active transmission, until the new season's vaccines become available; however, this would require regulatory changes, as providers cannot administer an expired vaccine," the researchers wrote.
"Another, somewhat more cumbersome solution would be to use Southern Hemisphere influenza vaccines as travel vaccines for cross-hemisphere travelers, which would also take into account the fact that travelers to the Southern Hemisphere may face influenza viruses not included in the Northern Hemisphere influenza vaccine," they added.
