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Vaccination: defence is the best attack
With the competitive season looming, Andrew Hamilton examines the current best thinking on vaccination for athletes, and makes recommendations for sports clinicians.
Without doubt, vaccination is one of the greatest triumphs of modern medicine. Many serious diseases that used to routinely maim or kill large numbers of people are no longer a threat. More than that, vaccination can prevent outbreaks of less serious illness, which although not life threatening, are still unpleasant, leading to missed time from work and school.
Anyone with young children or who has travelled extensively abroad will (hopefully) understand that a programme of vaccination is either required or recommended. When it comes to the travelling athlete however, the situation is rather more complex. While the basic vaccinations (eg typhoid, hepatitis etc when travelling to certain regions of the tropics) are of course still required, clinicians will also want to ensure that their athletes stay as well as possible to compete at their full potential. A mild illness that is an inconvenience to a tourist may be a disaster for an athlete focusing on the peak of his/her season!
Sports clinicians may therefore wish to consider extra vaccinations to minimise the risk of more minor conditions. However, this approach raises a whole new set of issues. For example, which additional vaccinations may be use for athletes who regularly travel abroad? What are the possible side effects of these extra vaccinations and how should vaccines be timed to maximise immunity during the competition, while minimising disruption to training in the run up to competition?
Athletes are different
There exists some uncertainty about the most appropriate vaccination regimens in athletes among team doctors and other physicians because general public health vaccination guidelines cannot be easily transferred to elite athletes. Complicating factors include the typical circumstances of athletes’ daily life, such as frequent travelling to foreign countries or close contact with teammates and opponents, which might indicate the need for a modification of recommended vaccination schedules. In addition, intense physical activity of training and competition with its possible effects on the immune function can affect decisions about execution and timing of vaccination.
Other complicating factors are that vaccination recommendations are formulated around a public health policy rather than for specific individuals and are likely to change over time(1-3). Also, there’s the issue of cost effectiveness; the majority of vaccines that are not generally recommended are not recommended because the medical benefit is not regarded sufficiently balanced with the costs if implemented across the whole population. This is despite the fact that they may be potentially beneficial in specific individuals(4,5). It’s also important to understand that generalised recommendations take no account of the implications of the effects of illness in athletes, which can be far more profound and far reaching than in the general public (see box 1).
Box 1: Illness impact on athletes
Infections have a different significance in competitive sports. For elite athletes, even mild diseases that would never cause absenteeism in the general population can be very detrimental to an athlete’s individual performance. Seemingly trivial infections might well impair general well-being (or the athlete’s perception of being perfectly prepared) and therefore represent a psychological obstacle for the realisation of maximal performance. Also, with the knowledge of a player’s infection, team coaches may tend to leave them on the bench, ‘just to be on the safe side’.
The same is true for long-lasting infections and post-infectious periods, without full recovery of physical performance. When white-collar workers have already returned to work, elite athletes are still performance impaired, or even unable to train and compete. Furthermore, some infections such an influenza, which typically cause only mild-moderate illness, can (in rare cases) result in severe complications such as myocarditis. Also, evidence suggests that during particularly strenuous training and competition, illness can make athletes potentially more prone to organ infections than their sedentary counterparts(6-8).
Further reasons as to why athletes are different when it comes to vaccination include the following:
- Athletes are often in close contact with opponents and teammates, which increases the risk of transmission of many diseases, particularly respiratory-transmitted diseases(9,10). Typically, a contact of less than 1–2 metres distance is necessary to transmit diseases such as influenza or other respiratory-transmissible agents such as varicella(11,12).
- For blood-borne diseases, the transmission risk due to sport is less pronounced but athletes are still at higher risk than the general population(13,14).
- Even healthy non-vaccinated athletes being exposed to an infectious agent (eg contact with a diseased individual) may have to be excluded from training and competition for medical reasons. Usually, such an exclusion has to last for the complete incubation period of a disease, which may be up to three weeks.
Putting all these factors together, the recommendation is that elite, competitive athletes should be vaccinated more aggressively than the general public(15).
The decision as to which vaccinations are given prior to foreign travel will depend on a number of factors, including the travel destination(s), the nature of the sport and the health/vaccination history of the individual involved. Regardless of these factors however, it is recommended that ALL adult athletes are routinely vaccinated against the following:
- Pertussis (whooping cough)
- Hepatitis A and B
- Measles, mumps and varicella (if immunity is not already proven by a natural infection)
Of these, numbers 1-5 should be given as inactivated vaccines while measles, mumps and varicella (chickenpox) should be given as live vaccines(15). A full discussion on the detailed considerations regarding each and every possible vaccination is beyond the scope of this article (readers are directed to a full and recent review of this topic by Luke and D’Hemecourt(15)). However, table 1 summarises most of the key recommendations.
Table 1: Some of the key vaccination recommendations for athletes(15)
|Disease||Geographical incidence||Risk of contraction||Possible vaccination side effects or drawbacks||Other considerations|
|Diphtheria and tetanus||Widespread||Increased in sports where bodily contact with soil and dust cannot be avoided, as well as the occurrence of wounds, both of which might favour the acquisition of Clostridium tetani.||Increased in sports where bodily contact with soil and dust cannot be avoided, as well as the occurrence of wounds, both of which might favour the acquisition of Clostridium tetani.|
|Pertussis (whooping cough)||Widespread||Reported as less than 1 in 500 per year, but this risk can be reduced by 90% for 2-3 years with vaccination – an important consideration bearing in mind the severe symptoms of the respiratory system that might last for many weeks and months.||Some adverse side effects are sometimes reported. However, pertussis vaccination is recommended in athletes because the likelihood of acquiring a severe, long-lasting infection that interferes with training and competition is relevant, and the vaccine-associated side effects seem tolerable.||At present, vaccination against pertussis in adults is only feasible using a combined vaccine together with tetanus and diphtheria booster dose(22).|
|Influenza||Widespread||High, especially as influenza vaccination may not protect against all strains in each season, which means that contact with vaccinated individuals may still be risk.||Temporary pain and/or swelling at injection site. Some patients report feeling a general sensation of feeling ‘unwell’ for a few days following vaccination.||Bear in mind that different vaccines might be recommended in the northern and southern hemispheres and that the influenza season differs considerably due to the climate in the two hemispheres. This means that influenza can be a risk year-round, and even outside of the typical influenza season when travelling to countries with differing influenza seasons. Given the above, a twice-yearly vaccination is essential for optimal protection.|
|Hepatitis A||Widespread||A mainly food-borne disease typically leading to some months of reduced physical performance. Difficult to prevent using simple measures(23). Higher prevalence in countries with moderate climate and poor hygiene levels. Due to the worldwide food market, even regions with typically low endemicity, such as Northern Europe, can be affected(24).Can be easily transferred to teammates and opponents.||Almost impossible to prevent hepatitis A virus infection by exposure prophylaxis alone; therefore vaccination is recommended.|
|Hepatitis B||Highly prevalent in Africa, parts of Asia, and Latin America||Mainly transmitted by blood or genital secretions. Viral load in infected individuals is rather high, enabling transmission even when only small amounts of infected fluids are transmitted. Vaccination is therefore relevant in all sports with possible contact to blood and body fluids, such as football, boxing, and hockey, but less so in sports such as tennis or most winter sports. Contact with the healthcare system in high-risk countries may pose an additional risk||Hepatitis B vaccination is strongly recommended in athletes because of the disease severity (typically several months of no or reduced training and competition eligibility complicated by irreversible organ damage) and its contagious nature Different hepatitis B vaccines with various hepatitis B surface antigen (HbsAg) concentrations (10, 20,and 40 micrograms) are available. For healthy athletes, a 20 microgram dose without adjuvant AS04 seems to be sufficient to confer immunity.|
|Measles, mumps and varicella (chickenpox)||Widespread||Measles is an extremely contagious and potentially severe disease with a high rate of complications such as pneumonia, otitis, encephalitis. Its high basic reproduction number (number of other infections that one case of measles generates on average over the course of its infectious period) means that even a short-lasting contact (eg with employees in hotels, shops, contact on streets) might result in an infection. Mumps and varicella are less contagious and severe in nature but like measles, have a more severe course in adults compared with children. This is particularly true for varicella where pneumonia and bacterial superinfection can occur as complications, and mumps, where meningitis is a possible complication.||All three vaccines should be administrated as live vaccines at least twice in non-immune individuals, with a minimum interval of 4 weeks between vaccinations(25). It is recommended to use combined vaccines whenever possible. In some countries such as the UK, measles and mumps are given as childhood vaccinations combined with rubella (see below).
Vaccinations recommended due to epidemiological reasons
|Disease||Geographical incidence||Risk of contraction||Possible vaccination side effects or drawbacks||Other considerations|
|Tick-borne encephalitis, yellow fever, Japanese encephalitis (see also box on mosquitoes and ticks)||*Tick borne encephalitis – some parts of eastern, central and northern Europe, northern China, Mongolia, and the Russian Federation|
*Yellow fever - Africa and some tropical parts of South America
*Japanese encephalitis- China, the Russian Federation’s south-east, and South and South-East Asia (including India and Nepal)
|Risk depends on exposure to ticks (see box on ticks)||Some individuals may experience mild side effects such as headache, muscle pain, a mild fever and soreness at the injection site. Effects usually occur one to five days after being vaccinated and may last for up to two weeks.|
|Poliomyelitis||Rare but does exist in a few countries such as Afghanistan, Pakistan, and Nigeria (physicians should check for latest health advisory updates)||Without direct contact with these countries (or indirectly through teammates), the risk of acquiring this infection is fairly low(26)||The vaccine to be chosen for athletes should be the same as recommended by the national guidelines for the general population.|
|Rubella||Widespread||Causes a much milder disease compared with measles or mumps and is mainly asymptomatic, with a rash as the most prominent manifestation, which is difficult to distinguish from allergic reaction. Fever and other complications are rare The main goal of vaccination is to reduce the risk of embryopathy in pregnant women||A possible side effect of vaccination in adults is arthritis for some weeks/months afterwards(27,28). This risk seems higher in women than in men. Regardless, the risks and benefits of rubella vaccination have to be considered carefully in an athlete, where arthritis might be considered a more severe problem than in the general population|
|Typhoid||Several Asian regions of Russia and neighbouring countries, and in parts of south and southeast Asia, Africa, and South America||The travel habits of elite athletes, and the fact that these bacteria are mainly transmitted in the setting of poor hygiene means that the risk of transmitting the bacteria is quite small||The oral vaccine occasionally has side effects that mainly consist of abdominal discomfort, nausea and vomiting whereas with the parenteral vaccines the local reactions at the site of injection dominate(29). Theoretically, the live vaccine’s effect can be diminished by the use of antibiotics. It is thus recommended that this vaccine should be administered at least 24 hours after any antibiotic medication(30).||At present, three different vaccines are available: an oral live-attenuated vaccine (Ty21a strain of salmonella typhi), a parenteral inactivated vaccine (Vi polysaccharide vaccine, one dose), and a more recently licensed capsular polysaccharide vaccine (Vi-rEPA, two doses) for parenteral use. Efficacy seems to be higher using the new vaccine (75 % seroconversion) compared with the two others (*50 %)(31,32).|
|Meningococcal Disease||Important when travelling to countries with high endemicity (sub-Saharan Africa from Senegal to Ethiopia).||Meningococcal vaccination is relevant since sporadic meningococcal meningitis with complications may develop in healthy individuals, with a high fatality rate of 10–50%. The disease peaks in children over 6 years of age and in adolescents and young adults. Vaccination is therefore particularly important for young athletes||A conjugate and a polysaccharide vaccine are available. Both vaccines cover the same subtypes but immune response to conjugate vaccines is much better, clearly favouring this type(33). Vaccination against meningococcal disease with a conjugate vaccine covering the serotypes A, C, W135, and Y is recommended when travelling to endemic areas(34-36).|
Vaccinations not relevant to athletes
|Cholera||Vaccination against cholera does not seem to be relevant since cholera is a disease associated with a very poor hygiene level, classically confined to refugee camps or slums.|
|Rabies||Rabies vaccination is not recommended since the vaccine has a high number of considerable side effects and the disease might be prevented by exposure prophylaxis. It should be possible to prevent animal bites in athletes by other measures and, when an incident occurs, post-exposure prophylaxis can be administered even after the bite.|
|Herpes zoster||Vaccination against herpes zoster (shingles) does not seem to be indicated since herpes zoster is only very rarely found in athletes. There are some anecdotal reports of zoster occurrence in endurance athletes during highly strenuous training periods. However, due to their scarcity, no conclusion of compromised immunity in this particular athlete population (as a typical precondition for zoster) can be drawn. Also, this vaccine was introduced only a short time ago and thus it is too early to draw any conclusions on a population for which the vaccine has not been tested so far.|
Insect-borne disease prevention in athletes
No discussion on vaccination and disease prevention would be complete without a mention of insect-borne disease risk, the main risk being from mosquitoes and ticks.
Mosquitoes–Athletes may assume that the only significant risk from mosquitoes is that of malaria when visiting certain tropical areas. However, mosquito-borne diseases also include West Nile virus, yellow fever virus, and dengue virus, which may occur outside of the tropics. In the US for example, West Nile virus has demonstrated a seasonally endemic epidemiology with especially in California, Arizona, and Colorado(16). This disease typically presents between July and October, although cases have presented between April and December.
Regardless, the prevention of mosquito bites is the cornerstone of prevention. An athlete in an endemic area should wear an insect repellent such as deet (N,N-diethyl-mtoluamide), picaridin (KBR-3023), or oil of lemon eucalyptus (p-menthane-3,8 diol). Deet and permethin may also be applied to the clothing. If a sunscreen is used simultaneously, the insect repellent should be applied on top of the sunscreen and removed at the end of the day. Long-sleeved shirts that are tucked into long trousers are also useful.
Ticks – Tick-borne diseases include rickettsial diseases, Lyme disease, babesiosis, tick-borne relapsing fever, and occasionally, tularemia and Q fever. Certain athletes who participate in rural outdoor activities are more susceptible to tick bites. These sports include cross-country running, training in multiple sports in rural areas, and recreational outdoor sports such as hiking.
The risk of each type of tick-borne disease will depend on the infectious organisms responsible for these illnesses and their particular lifecycles in ticks. For example, in the UK, Lyme disease is a real risk with an estimated 2,000-3,000 new cases reported in England and Wales each year(17). In the US, common tick-borne dieases include Rocky Mountain spotted fever, human monocytotropic ehrlichiosis, and human granulocytotropic anaplasmosis(18). These potentially lethal diseases are difficult to diagnose because they often mimic viral syndromes with flu-like symptoms in the early stages. Indeed, studies suggest that as many as 60% to 75% of patients presenting with a tick-borne disease may be initially misdiagnosed(19,20).
There are no proven vaccines for some tick-borne illnesses, but all are preventable by careful vigilance and protection. Athletes should remain vigilant about their training and competition environment; ticks thrive in a wooded environment and at the edge of woods, with surrounding high vegetation. However, ticks are uncommon in well-mowed lawns. When training in wooded areas, light-coloured clothing is helpful to identify the tick. Long training bottoms tucked into tightly woven socks and closed training shoes will also help minimise exposure. Deet at 10% to 25% should be applied to the skin while Permethrin may be applied only to the clothing. Clothes should be removed, cleaned and dried after exposure – a tumble dryer is effective in killing ticks.
Athletes who have been training or competing in a tick-prone area should carefully check for ticks in the nymphal phase (the stage between larvae and adulthood), which may be as small as the size of a pin head. Areas to pay particular attention to include the athlete’s hair, ears, axilla, belly button, and legs. The technique of tick removal is critical. Tweezers with fine tips should be used very close to the skin and the tick pulled directly away. Squeezing the body of the tick may allow contamination of the disease into the host. In the case of Lyme disease, infection is not contracted until at least 24 hours of tick adherence; however, ehrlichiosis(another tick-borne disease in temperate climates) may transmit in less than 24 hours.
The routine use of preventive antibiotics is generally not indicated because less than 5% of bites are Lyme infected, especially with a flat tick. However, following a high-risk exposure (when the tick has been engaged for more than 24 hours and is engorged with blood), a single dose of 200 mg of doxycycline is believed to be effective(21).
Timing of vaccinations should be chosen in order to minimise interference with training and competition, and to ensure the immune reaction is not temporarily impaired. Inactivated vaccines generally cause side effects within two days following vaccination. This is in contrast to live vaccinations where the peak of side effects is most likely to occur after 10-14 days when replication of the vaccines is at a maximum. Unless a vaccination needs to be administered urgently, the best time therefore for vaccination is at the onset of resting periods – for example at the beginning of the winter off season.
When a vaccination has to be carried out within a training and/or competition period (eg influenza), there is no major medical problem with training undertaken shortly before or after vaccination. However, it is recommended to vaccinate shortly after a competition in order to make the period of time to the next competition as long as possible. Many vaccinations given via injection can cause local pain and inflammation at the injection site. Clinicians may therefore wish to time vaccine administration so as to not coincide with delayed onset muscle soreness (DOMS) following strenuous exercise.
Dependent on the injection site, some sport-specific impairments may result (for example buttock pain in runners following a gluteal injection). Obviously, it is advisable to use the non-dominant side for injections in unilateral disciplines such as racquet sports. For vaccines that can be administered using either the intramuscular or the subcutaneous route, the intramuscular option seems to be preferable as it yields higher titer rate (more antibody production) and a lower risk of granuloma.
Injection into the deltoid muscle is preferred if possible, although other muscle sites are possible. Regardless, it is important that the athlete is sitting or lying, and the muscle is completely relaxed. Studies indicate that the use of longer needles (25 mm) and a fast speed of injection/withdrawal of the needle (1–2 seconds) are associated with less pain(37). Also, an angle of injection of 90 degrees may also help reduce pain in intramuscular injections.
Syncopes or collapses following vaccination are uncommon but may occur; some studies on influenza vaccination suggest the frequency of syncope in younger athletes to be around 1%(38). However, the syncope itself may be less important than secondary injuries caused by the collapse such as skull fracture and cerebral haemorrhage. Given that the majority of syncopes (80 %) occur within 15 min of vaccine administration, it is recommended that athletes are observed for a period of 15-30 minutes following vaccination. This recommendation may be particularly important for endurance athletes because there are indications that, in these athletes, vasovagally-induced syncopes are more frequent(39).
The recommended vaccination schedules for disease prevention will be dependent on the previous vaccination record and disease history of the athlete in question. Also, some schedules are dependent of the type/brand of vaccines used and recommendations may also differ according to public health policy in each country. Readers are directed to the summary given by Luke and D’Hemecour(15); there are also some excellent downloadable resources on the US Centre for Disease Control and Prevention (CDC) – https://www.cdc.gov/vaccines/schedules/hcp/adult.html.
The vaccination requirements for elite athletes are not the same as that for the general public. Not only are these athletes potentially exposed to more disease pathogens as a result of international travel, even the mildest episode of illness that would be barely noticeable to most of us can be devastating for elite athletic performance. For these reasons, sports clinicians and doctors should take a much more aggressive approach to vaccination of their athletes. Together with steps to reduce exposure and the correct vaccination techniques and timing, clinicians can maximise the potential of their athletes to perform at all times of year across all regions of the globe.
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