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Vaccination for athletes: it’s not just about covid-19

With the competitive season looming, Andrew Hamilton examines at the current best thinking on vaccination for athletes

As the rollout of covid-19 vaccination programs gathers pace across the globe, the subject of vaccines has never been more topical. At the time of writing, the early data emerging from these programs suggests that the current range of covid-19 vaccines are proving very effective at reducing the incidence and severity of illness, the mortality rate among vulnerable patients and also positively impacting transmission rates. The Pfizer/Biontech mRNA vaccine for example has shown 92% effectiveness according to data from Israel, the first country to roll it out widely [Maccabi Health Services & Times of Israel 25th January 2021].

Travel and vaccination

Although fit and healthy athletes rarely develop serious illness as a result of covid-19 infection, the potential to carry the virus asymptomatically and thus spread it to those who are more vulnerable is a problem. Even assuming covid-19 vaccines are rolled out quickly widely worldwide – thus protecting the vulnerable – the likelihood is that many countries may insist that overseas travelers are able to demonstrate they have been vaccinated against covid-19 before entry in the country. This is particularly likely to be the case for countries such as Australia and New Zealand, whose endemic rates of covid-19 have remained extremely low due to the early imposition of strict travel and quarantine arrangements.

With all the focus on covid-19 vaccinations however, athletes who intend to travel abroad and those who care for athletes should not forget the bigger picture, which is that there a large number of infectious diseases across the globe (some of which are far more threatening to an athlete’s health) that have most definitely not gone away! When considering travel vaccination therefore, it is imperative that athletes consider carefully all the vaccinations that are relevant, and not just focus on covid.

Athletes are different

Anyone with young children or who has traveled extensively abroad will (hopefully) understand that a program 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 – and now probably covid-19 too) are of course still required, athletes will also want to ensure that they stay as well as possible, even avoiding mild illnesses, in order to compete at their full potential. That’s because while a mild illness is an inconvenience to a tourist, it may be a disaster for an athlete focusing on the peak of his/her season!

Athletes and sports clinicians may therefore wish to consider extra vaccinations to minimize the risk of more minor conditions. However, this approach raises a whole new set of issues. For example, which additional vaccinations are recommended for athletes who regularly travel abroad? What are the possible side effects of these extra vaccinations and how should vaccines be timed to maximize immunity during the competition, while minimising disruption to training in the run up to competition?

Complicating factors

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). This is highly likely to be the case for covid-19 vaccinations. 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 generalized 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 realization 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 causes 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, upon 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).

Which vaccinations?

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. As we’ve already mentioned, it is likely that a covid-19 vaccination will be required for international travel to a variety of destinations going forward. In addition, it is recommended that ALL adult athletes are routinely vaccinated against the following:

  1. Tetanus
  2. Diphtheria
  3. Pertussis (whooping cough)
  4. Influenza
  5. Hepatitis A and B
  6. 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 review of this topic by Luke and D’Hemecourt(15)). However, table 1 summarizes most of the key recommendations.


Table 1: Some of the key vaccination recommendations for athletes(15)

DiseaseGeographical incidenceRisk of contractionPossible vaccination side effects or drawbacksOther considerations
Diphtheria and tetanusWidespreadIncreased 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. Childhood vaccination programs reduce risk to low. However, in adults, a 10-yearly booster dose with a reduced diphtheria component (Td) is recommended. Although the risk of acquiring diphtheria is low, both infections are very severe and often associated with serious complications, which further justify their prevention by well-established vaccinations.
Pertussis (whooping cough)WidespreadReported 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(16).
InfluenzaWidespreadHigh, 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 AWidespreadA mainly food-borne disease typically leading to some months of reduced physical performance. Difficult to prevent using simple measures(17). 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(18).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 BHighly prevalent in Africa, parts of Asia, and Latin AmericaMainly 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)WidespreadMeasles 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(19). 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).
Tick-borne encephalitis, yellow fever, Japanese encephalitis *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 ticksSome 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.
PoliomyelitisRare 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(20) The vaccine to be chosen for athletes should be the same as recommended by the national guidelines for the general population.
RubellaWidespreadCauses 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(21,22). 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.
TyphoidSeveral Asian regions of Russia and neighboring countries, and in parts of south and southeast Asia, Africa, and South AmericaThe 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(23). 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(24).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 %)(25,26).
Meningococcal diseaseImportant 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.vailable. Both vaccines cover the same subtypes but immune response to conjugate vaccines is much better, clearly favoring this type(27). Vaccination against meningococcal disease with a conjugate vaccine covering the serotypes A, C, W135, and Y is recommended when travelling to endemic areas(28-30).

NB: 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.


Vaccination timing

Timing of vaccinations should be chosen in order to minimize 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.

Vaccination techniques

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(31). 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%(32). However, the syncope itself may be less important than secondary injuries caused by the collapse such as skull fracture and cerebral hemorrhage. 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(33).

Vaccination schedule

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.

Summary

The vaccination requirements for athletes are NOT the same as that for the general public. Not only are 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 sedentary people can be devastating for elite athletic performance. For these reasons, athletes, along with sports clinicians and their doctors should take more aggressive approach towards vaccination. Together with steps to reduce exposure, and the correct vaccination techniques and timing, the potential for athletes to perform at all times of year across all regions of the globe can maximized!

References

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