Because there is no evidence that travel is an additional risk factor for influenza, the Dutch guidelines for travelers health advice do not recommend influenza vaccination for travelers other than those at high risk of complications
Because there is no evidence that travel is an additional risk factor for influenza, the Dutch guidelines for travelers health advice do not recommend influenza vaccination for travelers other than those at high risk of complications. Conclusions We found that the attack rate of influenza in long-term travelers closely mirrors seasonal rates in the general population in temperate and tropical regions and travel was not a risk factor for severe disease. rate in this study is similar to seasonal rates of infection in the general population. Influenza vaccination pre-travel is therefore most important for people at risk of medical complications due to influenza. valuevaluevaluevaluevaluevaluevaluevalue throughout is Pearsons chi-squared; Significance assigned (*) at value /th /thead A/California/007/09 H1N1pdm6,22.6C14.40.000A/Brisbane/59/071,20.2C9.30.866A/Brisbane/10/073,61.1C11.00.028A/Perth/16/091,80.5C6.20.354B/Florida/4/061.0[??-][??-]B/Brisbane/60/081.0[??-][??-] Open in a separate window aOdds ratio of association between seroconversion with individual virus and complaining of ILI. Univariable logistic regression by virus Discussion In this young cohort of long-term travelers to (sub) tropical countries (2009 to 2012), the attack rate for confirmed influenza virus infection was 15?%. This is higher than the 1C7?% found in other, mainly short-term traveler studies [1, 12, 13] and closely mirrors seasonal rates of infection in the (unvaccinated) general population in temperate [14] and tropical [15] regions during the same period, reflecting the prolonged travel duration. For symptomatic infection, we found attack rates of 6.3?% (fever alone) and 2?% (ILI), respectively, which was higher than in two short-term studies that found attack rates of 0.9C1.3?% for confirmed infections with fever alone [1, 12] and 0.8?% for ILI [12]. The results of symptomatic infections however, should be interpreted with care. First, some studies use different definitions than ILI for symptomatic infections and do not report fever as the only symptom of confirmed infection [13]. Second, fever is a very common symptom in travelers [1, 12]. At the same time, confirmed infections without fever were found in 32 and Rabbit Polyclonal to DUSP22 83?%, respectively [1, 12]. Because virological data from nasopharyngeal sampling was not available for any of the MK-1064 studies, we can not be sure whether the symptoms were caused by influenza or by other infections. In our study, both the proportion of travelers with fever (35?%) and the proportion of travelers with confirmed infections without fever (58?%) were high. Therefore we did not calculate IRs for symptomatic influenza infections. As shown elsewhere [15], travelers in their mid-20s were more susceptible to A(H1N1pdm09) infection than other viruses. The majority of respondents were immune to at least one virus pre-travel, and 1/5th departing before the pandemic was declared were positive for A(H1N1pdm09) as early as January 2009. Forty percent of travelers were infected with 1 virus while traveling and 10 people experienced a reinfection. Travelers infected with A(H1N1pdm09) during travel were more likely to be symptomatic with ILI. Overall, the positive predictive value of ILI was 38?%. We found no evidence of seasonality or destination-specific risk, and travel was not a risk factor for severe disease. There were some limitations to our study. The pre-travel influenza vaccination status was not confirmed. However, in the Dutch healthcare system, it is very uncommon that healthy, young travelers are vaccinated. Another possible limitation is that travelers only measured their temperature MK-1064 if they felt feverish rather than daily. This may have lead to an underestimate of the proportion of travelers with fever, and an overestimate of the number of asymptomatic infections. Vaccination for travelers against influenza has been discussed [16]. In the USA, influenza vaccination is recommended for all US residents aged 6?months [17]. The USA guidelines for international travel (Yellow Book, MK-1064 2016) say any traveler who wants to reduce the risk for influenza infection should consider influenza vaccination 2?weeks before departure if they plan to travel to the tropics. According to WHO, influenza vaccination should be part of the routine immunization program for international travelers belonging to a risk group, in particular during influenza seasons [18]. In the Netherlands, only people at risk for complications are adviced influenza vaccination. Because there is no evidence that travel is an additional risk factor for influenza, the Dutch guidelines for travelers health advice do not recommend influenza vaccination for travelers other than those at high risk of complications. MK-1064 Conclusions We found that the attack rate of influenza in long-term travelers closely mirrors seasonal rates in the general population in temperate and tropical regions and travel was not a risk element for severe disease. Influenza vaccination pre-travel is definitely therefore most important for people at risk of medical complications due to influenza. Ethical authorization and consent to participate The study was authorized by the Medical Ethics Committee of the Academic MK-1064 Medical Center. Pre-travel, written educated consent was acquired form all participants. Consent for publication Not applicable. Availability of data and materials Data will become shared upon request. Identifying/confidential individual data however will not be shared. Acknowledgements We say thanks to the medical doctors and nurses of the Public.