Vaccines for travelling minors: The ‘shot’ heard around the world

Abstract

The number of adults, children and adolescents who travel from the industrialized world to less industrialized countries for work or pleasure is steadily increasing. Travel immunizations for children are a critical element of pretrip planning. Occasionally, one of the most daunting aspects of an exotic trip or a foreign posting can be the logistics (and recriminations) associated with getting the family to a travel medicine clinic with sufficient lead time to ensure that all of the necessary immunizations are given before departure. The present paper reviews pertinent immunization information from three points of view: the travel clinic, the parent and (with license) the child.

The number of people travelling from the industrialized world to less industrialized countries for work or pleasure is steadily increasing (1). Although many factors contribute to this trend, accessibility of airfares, the globalization of industry and changing immigration patterns are some of the most important factors. Children and adolescents are a major part of this travel trend for several reasons. Whole sectors of the travel industry now focus on attracting families with young children to exotic locations, and industrial, diplomatic and other postings of families overseas are increasing. In addition, immigrant families with young children are increasingly able to bring children born in the industrialized world ‘home’ to meet their extended families. Finally, students from the developed world have more opportunity to work and study abroad. Occasionally, one of the most daunting aspects of an exotic trip or a foreign posting may be the logistics (and recriminations) associated with getting the family to a travel medicine clinic with sufficient lead time to ensure that all of the necessary immunizations can be given before departure. The present paper reviews pertinent immunization information from three points of view: the travel clinic, the parent and (with license) the child. A comprehensive review of vaccines for children travelling was published recently (2).

THE TRAVEL CLINIC

The travel medicine clinic visit is an important part of pretrip planning to destinations outside of the ‘narrowly defined’ developed world (eg, North America, Western Europe, Australia, New Zealand and Japan). The verification of immunization records and a discussion of the schedule for appropriate travel vaccines are core functions of this visit. Immunization issues can be divided into two broad categories: those dealing with routine immunizations (ie, changes in schedule, additional doses, interchangeability of products or formulations) and those dealing with vaccines that are not routinely used in North America.

ROUTINE IMMUNIZATIONS

Among the routine immunizations that are used in North America, travel can impose schedule changes for measles vaccine and hepatitis B virus (HBV) vaccine.

Measles vaccine

In all jurisdictions in North America, measles vaccine is delivered twice during the first six years of life. Although the details of measles vaccination schedules vary among regions, the first dose is always combined with mumps and rubella vaccines (measles-mumps-rubella [MMR]) and is typically delivered between 12 and 15 months of age (3,4). The second dose of a measles-containing vaccine (measles, measles-rubella or MMR) is normally delivered between 18 months and six years of age. In the developing world, the World Health Organization recommends that measles vaccine (usually measles alone) should be administered at nine months of age or as early as six months of age in the setting of a measles epidemic (5). Children who will travel to the developing world between six and 12 months of age should receive their first dose of measles-containing vaccine (measles, measles-rubella or MMR) according to World Health Organization recommendations (ie, at nine or six months of age, depending on the epidemiology of measles at the destination country or region). These children should receive two subsequent doses of a measles-containing vaccine; the first dose should be given as soon as possible after 12 months of age, and the second dose should be given between three to six months later (15 to 18 months of age). At least the 12-month dose should contain mumps and rubella vaccines, as well. Although this regimen requires the administration of three doses of a measles-containing vaccine within a relatively short period of time, this intensity of vaccination is appropriate to optimize protection of infants at a time when they are the most vulnerable to serious complications from measles.

HBV vaccine

HBV vaccine can be successfully administered at the time of birth and at any time during childhood, adolescence or adulthood (6,7). The preadolescent HBV vaccines programs in developed countries reflect the predominant pattern of transmission in these societies (ie, teen sex and injection drug use) (8). However, even in North America, children considered to be at high risk (eg, the mother is a carrier of hepatitis B, or siblings or playmates are known to be hepatitis B surface antibody-positive) are vaccinated as soon as possible. Because HBV carrier rates are much higher in many regions of the developing world than the developed world (9), every effort should be made to arrange full HBV immunization for children of any age who will have significant contact with local residents in the developing world (eg, children of missionaries, children returning to their parents’ countries of origin for prolonged visits, or children attending day care or school abroad).

‘Extra’ doses of routine immunizations

With the exception of measles vaccine, there is no reason to give ‘extra’ doses of any other routine vaccine for North American children whose immunization booklets are up-to-date.

Interchangeability of different formulations for routine immunizations

Many different formulations for routine immunizations exist in different countries around the world. For example, there are at least 10 different formulations that can be used to immunize children against Haemophilus influenza type B (Hib). Many childhood immunizations require multiple doses to obtain optimal protection (eg, diptheria-pertussis-tetanus, Hib, HBV). Although it is ideal to complete any series of immunizations with the same formulation, travel plans cannot always be altered to ensure that this occurs. Occasionally, parents take it upon themselves to transport and store the appropriate dose or doses of vaccine, but this is seldom realistic and should be discouraged. Commercial vaccine antigens/formulations are all very closely related. Although few of the possible permutations and combinations have been rigorously evaluated, the data available (10,11) suggest that appropriately stored and administered vaccine antigens from different commercial sources can be substituted ‘mid-series’ with relative confidence.

VACCINES NOT ROUTINELY USED IN NORTH AMERICA

Table 1 contains a list of the available travel vaccines that may be appropriately considered for North American children and the recommended schedules, age restrictions, estimated efficacy, precautions and contraindications, and common side effects. As a general rule, children tolerate travel vaccines very well (once the needles are put away). The most common concerns that arise regarding these vaccines are the lower age limits and costs. Cost will be considered briefly in the section dealing with the ‘parental viewpoint’. Many travel vaccines have age limits below which they are thought to be unnecessary (eg, hepatitis A, typhoid), ineffective (eg, meningococcus in children younger than two years of age), of unknown efficacy (eg, Japanese B encephalitis) or potentially dangerous (eg, yellow fever in children younger than nine months of age).

TABLE 1:

Travel immunizations for children

Vaccine	Type	Age limits*	Estimated efficacy†	Precautions and contraindications†	Side effects§
Cholera	Attenuated	>3 years	0% to 100% (varies with serotype)	Hypersensitivity, immunocompromised, pregnancy	Diarrhea and/or vomiting
Hepatitis A	Inactivated	1 year	>95%	Hypersensitivity	Local reaction
Hepatitis B	Recombinant protein (hepatitis B surface antibody)	none	>95%	Hypersensitvity	Local reaction
Japanese B encephalitis	Inactivated	1 year	70% to 95%	Hypersensitivity	Local reaction, ‘late’ hypotension
Meningococcus	Polysaccharide	>3 to 6 months (varies with serotype)	90% to 95%	Hypersensitivity, loss of booster response¶	Local reaction
Rabies	Inactivated	None	>95%	Hypersensitivity	Local reaction
Tick-borne encephalitis	Inactivated	None	70% to 90%	Hypersensitivity	Local reaction, fever (in 3% to 20% of patients)
Typhoid	Attenuated	>3 to 5 years	50% to 60%	Hypersensitivity, immunocompromised, pregnancy	Diarrhea and/or vomiting (in 2% to 5% of patients)
	Inactivated	>2 years	50% to 60%	Hypersensitivity	Local reaction
Yellow fever	Attenuated	>1 year	>90%	Hypersensitivity, immunocompromised, pregnancy	Local reaction, fever (in 7% to 15% of patients), meningoencephalitis**

^*Age limits can be relative (ie, based on the ability of a young child to ingest oral typhoid or cholera vaccines) or more definitive (ie, such as an elevated risk of meningoen-cephalitis following yellow fever vaccination in children younger than one year of age) based on serious side effects in very young children;

^†For many travel vaccines, efficacy data are available only for adults or for populations living in endemic regions. As a result, the efficacy estimates presented for travelling Canadian children are rough estimates at best;

^‡Only selected precautions and contraindications are listed, and readers are referred to the product monograph or appropriate national or international guidelines for complete information;

^§Only selected side effects are listed, and readers are referred to the product monograph or appropriate national or international guidelines for complete information;

^¶Recent evidence suggests that children exposed to some polysaccharide antigens early in life may become refractory to subsequent repeat doses of the same antigen;

^**In immunocompromised patients, very young children (younger than one year of age) and, possibly, elderly individuals (older than 65 years of age)

Hepatitis A and typhoid are widely believed to be relatively innocuous illnesses in children younger than five years of age (12,13). In some cases, one can argue for the vaccination of very young children to reduce transmission to older family members who are more likely to suffer symptomatic illness. Although some controversy exists (14) and there are licensed formulations for children as young as two (typhoid) and one year of age (hepatitis A), there is little reliable information on which to base firm conclusions for the use of these vaccines in very young children. Gamma globulin can theoretically be given to protect children younger than one year of age against hepatitis A, but this is seldom done in clinical practice (15). Breastfeeding or the careful control of water used to prepare formula and foods can be adequate alternate approaches.

The relative inability of very young children to respond to polysaccharide antigens is well established. This immunological limitation underlies the recommendation for two doses of meningococcal (type A) vaccine in children who are at least one year of age and earlier repeat doses in children initially vaccinated (type A and C) before two years of age (16,17). Recently, data have accumulated suggesting that the vaccination of very young children (younger than two years of age) with meningococcal C vaccine may reduce the capacity of these children to respond to subsequent doses (ie, meningococcus C antigen-specific unresponsiveness) (18; NE MacDonald, personal communication). This issue may be resolved with the pending introduction of conjugate-meningococcal vaccines, although these products will, most likely, be much more expensive than current formulations (19). Finally, considerable care must be taken with families that propose to take very young children (younger than one year of age) to areas with high transmission rates of mosquito-borne illnesses (eg, Japanese B encephalitis, dengue fever, yellow fever and, of course, malaria). In some cases, appropriate counselling may lead to alternate travel plans. If parents cannot be dissuaded, a meticulous explanation of mosquito-prevention strategies may provide some measure of protection for these most vulnerable travellers (eg, pyrethroid-impregnated bed-nets, screens, residual pesticides such as permethrin and, possibly, the cautious use of low concentration N, N diethyl-m-toluamide [DEET]-containing repellents [eg, a concentration of 10% or less]) (20). Each of these potential interventions should be reviewed within the context of the severity of the illnesses that one is trying to prevent (ie, risk benefit analysis).

THE PARENTS

The most common travel immunization issues for parents visiting a travel clinic are ensuring optimal protection for their children (frequently with less disregard for their own safety) and the cost of the vaccines. Both issues typically arise when families with young children travel either to visit relatives or to make a religious pilgrimage (eg, to the Hajj). In the former case, it can take a great deal of skill (and time) to convince Canadians who were born abroad of their vulnerability to diseases such as Japanese B encephalitis, malaria and typhoid. Evidence suggests that only a small fraction of such families present to a travel clinic (21). In the latter case, the surprise of learning the ‘additional’ cost of the recommended or mandated travel vaccines (eg, meningococcal vaccine for travel to the Hajj, yellow fever for complicated itineraries) can lead to disbelief, shock and (rarely) disruptive behaviour. The cost of these vaccines can even result in the cancellation of travel plans for lower income families with many young children. Such cost issues are likely get worse in the near future as new vaccines are introduced and the average cost of these products increases (22). Both issues are essentially problems of information. All Canadian physicians need to be alert to the fact that immigrant families with young children do not routinely include the travel clinic in their pretrip planning. Right or wrong, the fact that travel vaccines are not ‘covered’ by public medical insurance plans is unlikely to change in the near future. As a result, the education of families with young children about the value of travel vaccines needs to begin as early as possible, ideally at the time that the referral to the travel clinic is made.

THE CHILDREN TRAVELLING

The vast majority of the children who appear in travel clinics are unenthusiastic (to say the least) about the entire process. The more sophisticated children will explain that no shots are required for their destinations of choice (eg, Disneyland, the neighbourhood amusement park). The less sophisticated children simply scream. The saddest (and often the most hysterical) children are those who perceive the coming trip and/or foreign posting as the ‘end of life as they know it’. While most of these problems are clearly family affairs, they can have a significant effect on the smooth functioning of a travel clinic. Although the author is not aware of any formal studies, blood-curdling screams emanating from the vaccinator’s office cannot be good news for those in the waiting room. Education is once again a critical factor, particularly the transmission of information at the time of the referral to the travel clinic. It is amazing how many parents spring the travel clinic visit on their ‘high strung’ children. Referring physicians can do everyone (eg, children, parents and vaccinators) a great service by initiating the conversation about ‘shots’ well in advance of the clinic visit. Although the large majority of children will respond to compassion and reasoned arguments (ie, good parenting), early discussion may permit the identification of the few children who are likely to ‘melt down’. The parents of these children may be advised to add the anesthetic effects of EMLA (AstraZeneca Canada Inc, Canada) cream to their arguments (it is applied to the appropriate area of skin 30 to 45 min before arrival at the clinic). Recent evidence suggests that this topical anesthetic cream can be used in conjunction with both live-attenuated and inactivated childhood vaccines without loss of efficacy (23,24). Although no data exist for the use of EMLA with travel vaccines, there is no reason to believe that such use will result in either increased side effects or loss of potency.

CONCLUSIONS

Travel immunizations for children are a critical element of pretrip planning. Issues of vaccine accessibility and cost are likely to become more prominent in the coming years as new and more costly products are introduced. A great deal of work remains to be done to ensure that all Canadian children travelling abroad receive optimal immunization. All Canadian health professionals have a role to play in this effort.