Should health-care providers in the United States have access to influenza vaccines formulated for the southern hemisphere?

Background: Influenza is the most common vaccine-preventable disease in travelers. It circulates year-round in the tropics, November to March in the northern hemisphere (NH), and April to October in the southern hemisphere (SH). In 2005, approximately 8.5 million US adults aged 18 years and older traveled to the Caribbean. A similar number traveled to the tropics and the SH. SH formulation of influenza vaccine is not available in the United States. We surveyed International Society of Travel Medicine (ISTM) members to ask if they would use SH influenza vaccine if available.

Methods: We electronically mailed a survey in December 2006 to 1,251 ISTM members in the United States. We asked if respondents would use SH vaccine for patients traveling to the SH or tropics, how many such patients per week they see, and their practice location.

Results: We received 157 responses for a response rate of 12.5%. Of these, 129 (82%) stated that they would be interested in having SH influenza vaccine available. Of those indicating interest, 73 (60%) reported seeing >10 patients traveling to the SH or tropics each week. Respondents reported practice settings in 34 states and the District of Columbia. Respondents requested more information about the likely cost of SH influenza vaccine, ordering conditions, vaccine use guidelines, comparability with NH vaccine, and approval of SH vaccine by the Food and Drug Administration.

Conclusions: Many travelers to the SH are at risk for influenza infection. Although only a limited number of ISTM members responded, respondents indicated considerable interest in availability of SH influenza vaccine for their patients. More data from travel medicine and other practitioners are needed on this topic. Inquiries are being made of influenza vaccine manufacturers about licensing SH influenza vaccines in the United States. Adding SH influenza vaccine to the vaccines available to NH clinicians could help mitigate the morbidity of influenza in travelers.