Clinical: MMR boosters for travellers

Dr David A Ross and Dr Rachel Pudney summarise the current advice on mumps and measles for travellers.

Mumps, measles and rubella remain important diseases globally and unprotected travellers may be at risk in areas where they are endemic.

Unproven scares in the past decade about the safety of the combined MMR vaccine mean that many travellers may not be protected. Those born in the UK before 1960 have never been offered the MMR vaccine. An outbreak of measles in North Korea in 2006 emphasises the potential risk.

Measles

While measles is now rare in most industrialised countries, it is common in many developing countries. More than 20 million people are affected each year, and with around 945 measles-related deaths a day in 2005.

The majority of measles deaths occur in countries with a per capita gross national income of less than $1,000. The primary reason for continuing high childhood measles morbidity and mortality is the failure to deliver at least one dose of measles vaccine to all infants.

Measles is an acute viral illness caused by a paramyxovirus and is one of the most contagious diseases known. The first sign of infection is usually a high fever 10 to 12 days after exposure that lasts one to seven days. The patient may develop coryza, cough, red and watery eyes and small white Koplick spots inside the cheeks.

After several days, a rash develops, usually on the face and upper neck, and after about three days the rash proceeds downward, eventually reaching the hands and feet, lasting approximately six days. Patients are infective for four days before the onset of the rash until four days after the rash fades.

Severe measles is particularly likely in poorly nourished young children, especially those deficient in vitamin A, or whose immune system has been weakened by HIV/AIDS or other diseases.

Children usually do not die directly of measles, but from its complications.

Complications are more common in children under five and in adults over 20.

The most serious complications include blindness, encephalitis, severe diarrhoea and otitis media. However, pneumonia is the most common cause of death associated with measles. Patients who recover from measles are immune for the rest of their lives.

Mumps

There are approximately 30 million cases of mumps and over 900,000 deaths every year globally.

The number of notifications in England and Wales has increased dramatically in the past decade, to the extent that it has been classed as a nationwide epidemic.

Mumps is a respiratory infection caused by a paramyxovirus, with an incubation period of approximately 18 days. Patients will probably be ill for 7-10 days. Of those infected, 60-70 per cent will develop symptoms, 90 per cent of whom will develop a parotitis - unilateral or bilateral - and 40-50 per cent non-specific respiratory symptoms.

Individuals are infective three days before the parotitis and up to five days after the onset of swelling.

Most people recover from mumps without many problems but a significant number will develop serious complications. The likelihood of complications increases with age and includes orchitis (although sterility is rare), meningitis, deafness and encephalitis.

Contracting mumps in the first trimester of pregnancy increases the risk of miscarriage.

Rubella

Rubella remains an important disease because of the risk of congenital rubella syndrome (CRS). Rubella is a respiratory-acquired infection caused by a togavirus. There is a mean incubation period of 14 days and the clinical presentation consists of a maculopapular rash 14-17 days after exposure, fever, lymphadenopathy, arthralgia or arthritis, and conjunctivitis.

If the mother is exposed in the first trimester the risk of CRS is 85 per cent. Other major complications include thrombocytopenia and encephalitis.

CRS covers a spectrum from intrauterine death to severe disability, including cataracts, deafness, cardiac defects, micro-cephaly and severe learning impairment. There are approximately 110,000 cases of CRS globally per year. In the UK, around 50 terminations are performed annually for CRS.

Risks to the traveller

The risks should be considered to the individual and to the community.

While an unprotected individual puts him or herself at risk of the full spectrum of disease described above, importing infections into their native country poses a serious public health threat to those who are unprotected.

In England and Wales 23 per cent of the sporadic cases of measles notified in the period 1995-2001 were imported.

As part of the general travel history the basic national immunisation record of the traveller should be taken.

For most developed countries, including the UK, this will include having been offered two doses of MMR in childhood, with the primary dose at 12-15 months and the booster dose three years later.

For those that have not had two documented doses and are travelling to endemic areas the opportunity should be taken to offer MMR vaccination.

MMR vaccine

The two-dose MMR vaccination was introduced in the UK in 1996. MMR contains live attenuated strains of the measles, mumps and rubella viruses and consideration must be given to the timing and administration of other live vaccines.

There are few contraindications to MMR vaccination but they include anaphylactic reaction to previous vaccines containing measles, mumps or rubella, immunosuppression, pregnancy, and anaphylactic reaction to neomycin or gelatine.

Although routine MMR vaccination starts at 13 months in the UK, infants over six months who are travelling to endemic areas should be vaccinated.

However, they should still receive their two-dose course as normal on their return, because there is a suboptimal response to vaccination at such a young age.

Children who have already received their first dose should have their second dose before travelling, assuming one month has passed since their first dose. If they are younger than 18 months when vaccinated the second time they should also receive their pre-school booster.

Older children and adults who have not completed a two-dose schedule should be assessed regarding their previous vaccination history (MMR or the MR vaccine), likelihood of childhood exposure to natural infection (such as those born before 1970), and risk of exposure when travelling.

The aim is to ensure immunity in those at risk. Where an incomplete vaccination history is given by an adult it is better to err on the side of caution and offer MMR vaccination.

If travellers do not have a history of adequate protection against these diseases, then previous immunisation status should be obtained, whether or not international travel is planned. The fact that a person is seeing a travel health provider or a primary healthcare provider for immunisations for travel should act as a signal to take the opportunity to vaccinate where there are gaps in routine coverage.

- Dr Ross is consultant public health physician at MASTA, London and Dr Pudney is a student at the London School of Hygiene and Tropical Medicine.

KEY POINTS

- Unprotected travellers to areas where mumps, measles and rubella are endemic put themselves at risk of acquiring these infections. They may also pose a public health threat on return to their native country.

- Measles is one of the most contagious diseases. Severe complications include blindness, encephalitis, diarrhoea and otitis media. Pneumonia is the most common cause of death.

- The incidence of mumps in England and Wales has increased dramatically in the past decade. Complications include orchitis, meningitis, deafness, encephalitis, and an increased risk of miscarriage if contracted in the first trimester of pregnancy.

- Rubella remains an important disease because of the risk of congenital rubella syndrome to the unborn fetus.

- Travellers' previous vaccination history should be assessed. Those who have not had two documented doses of MMR vaccine who are travelling to endemic areas should be offered MMR vaccination.

- Infants over six months who are travelling to endemic areas should be vaccinated.

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