Polio Vaccination

This article covers mainly the UK perspective on polio vaccination. For worldwide information, see the further information section. See also the related articles Poliomyelitis and Post-polio syndrome.

Infection with polio virus occurs through the gastro-intestinal route. In most cases (about 95%) it produces a mild and harmless infection. However, it may cause meningitis, paralytic illness or encephalitis. The paralytic form occurs because the virus invades motor neurones in the anterior horn of the brainstem and spinal cord. This may be fatal or may lead to permanent muscle weakness and disability.

The infection is transmitted through contact with the faeces or pharyngeal secretions of an infected person.

In the past, polio was endemic in the UK and many countries; there were epidemics during the 1950s. Immunisation programmes were introduced from 1956; since then, the number of cases has largely reduced. Many countries, including the UK, are now thought to have eliminated the polio virus. However, polio is still endemic in some developing countries. Polio infection can also occur (rarely) from the live vaccine (see below).

Types of polio virus infection

Wild virus:

• The naturally occurring polio virus is known as 'wild virus'. It is the wild virus that causes paralytic polio in countries where the infection is endemic. There are 3 subtypes of polio virus.
• Infection with wild poliovirus gives lifelong immunity, but only to the particular subtype involved (types 1, 2 or 3).

Polio associated with vaccines:

• Vaccine-induced paralytic polio (VAPP):
  • Rarely, the live attenuated vaccine virus in the oral polio vaccine (OPV) can cause paralysis - either in the vaccinated child, or in a close contact. Immune deficiency of the recipient may contribute. This occurs in about 1 in 2.5 million doses of the vaccine.
• Vaccine-derived polioviruses (VDPVs):
  • Also rarely, a strain of poliovirus in OPV may genetically change so that it can both cause paralysis and circulate among a population. These are known as vaccine-derived polioviruses (VDPVs).

Polio vaccines

Oral polio vaccine (OPV):

• Also known as the Sabin vaccine.
• It comprises live attenuated strains of poliovirus 1-3.
• Advantages:
  • Cheap; orally administered.
  • Promotes antibody formation in the gut; this protects more effectively against wild polio infection and reduces transmission of the wild virus.
  • Provides community benefit because the vaccine virus is excreted; therefore the contacts of recently immunised children may, in effect, get a second-hand dose of the vaccine.
  • It is therefore used to contain outbreaks, and for eradication where polio is endemic.
• Drawbacks:
  • Small risk of vaccine-related polio (VAPP or VDPV, above). The VAPP risk may be higher for immunocompromised patients.

Inactivated polio vaccine (IPV):

• Also known as the Salk vaccine.
• Contains inactivated strains of polioviruses 1-3.
• Advantage: no risk of vaccine-related polio.
• Disadvantage: does not stimulate antibody in the gut, so less effective against wild poliovirus.
• Protects only the immunised person; no community benefits.

The decision nationally as to which vaccine to use depends on the balance of various risks:

• The risks of wild polio virus being imported - if this is high, favours OPV.
• The risks of VAPP from OPV use.
• The efficacy of IPV.

Since 2004, this balance favours IPV for routine immunisation in the UK.

Polio vaccination in the UK

• In the UK, immunisation started in 1956 using IPV. This was replaced by OPV from 1962.
• From 2004, the UK switched back to using IPV.
• IPV is normally given in combination with tetanus and diphtheria vaccines (see 'Immunisation schedule in the UK' below).
• UK coverage (2004-5) was around 94% by the child's second birthday.³

2-8 °C, protect from light, discard if frozen. Shake the vial before use.

Altogether, five doses of IPV are required. These are given in the following schedule. Further details are in the British National Formulary.⁴ Note that different preparations are used before/after age 10 years.

Children age 2 months-10 years

• IPV is part of the diphtheria/tetanus/pertussis/polio/Hib vaccine. It is also available without the haemophilus component for children > 3 years.
• The primary course comprises three doses given one month apart. This is usually started at age 2 months.
• A first booster dose is given 3 years after the primary course (usually as the 'pre-school booster'). The 3-year interval can be reduced to 1 year if the primary course was delayed.

Children > 10 years and adults

• IPV is given as the diphtheria/tetanus/pertussis/polio vaccine (using a lower diphtheria dose, and without the haemophilus component, in this age group).
• The primary course (for those not previously immunised) comprises three doses given one month apart.
• A booster dose is given 3 years after the primary course (the 3-year interval can be reduced to 1 year if the primary course was delayed).
• A second booster dose is given 10 years after the first booster (usually given during the teenage years). The 10-year interval can be reduced to 5 years if previous doses were delayed.

Notes²

• If the primary course is interrupted, it should be resumed but not repeated, allowing an interval of one month between the remaining doses.
• Those who commenced vaccination with oral polio vaccine can complete the course with IPV-containing vaccines.
• If a person attends for a routine booster dose and has a history of receiving a vaccine following a tetanus-prone wound, attempts should be made to identify which vaccine was given. If the vaccine given at the time of the injury was the same as that due at the current visit and was given after an appropriate interval, then the routine booster dose is not required. If not, the dose given at the time of injury should be discounted (it may not provide adequate protection) and the scheduled immunisation should be given.
• For children coming from abroad, guidance is given in The Green Book.²

Travel

Travellers to epidemic or endemic areas should ensure they are fully immunised according to the UK immunisation schedule (above). Additional doses of vaccines may be required, depending on the destination.

The inactivated polio vaccine (IPV) can be given to immunosuppressed patients, e.g. those with HIV and premature babies:

• The normal schedule should be followed.
• However, these individuals may not make a full antibody response. Re-immunisation should be considered after treatment, and specialist advice may be needed.

IPV can also be given to pregnant and breastfeeding women, if protection is required without delay. There is no evidence of risk from vaccinating pregnant or breastfeeding women with inactivated vaccines or toxoids.

Anaphylaxis:

• The contra-indications are:
  • Confirmed anaphylactic reaction to previous IPV vaccine (very rare).
  • Confirmed anaphylactic reaction to a vaccine component (neomycin, streptomycin or polymyxin B).
• If in doubt, seek advice from a consultant in paediatrics or infectious diseases, rather than withholding immunisation.

Neurological conditions:

• Neurological conditions are not a contra-indication to immunisation. However, the timing of immunisation depends on whether or not their condition is stable. Detailed advice is in The Green Book.²

Concurrent illness:

• Minor illnesses without systemic upset do not require postponing the immunisation.
• For anyone acutely unwell, immunisation should be postponed until full recovery. This is to avoid confusing the effects of the illness with any adverse effects of the vaccine.

Report adverse reactions to CSM via the Yellow Card Scheme.

• Pain, redness and swelling are common.
• Transient nodule at the injection site.
• Anaphylaxis is rare (0.65-3 per million).

For any suspected case of polio infection:

• Report immediately to a consultant in communicable diseases (polio is a notifiable disease).
• As explained above, the OPV vaccine (not IPV) is normally used in outbreaks.
• To prevent ongoing transmission, OPV should be given immediately to household contacts of those with suspected polio. Other people in the neighbourhood of the case may also require OPV.
• A supply of OPV will be issued on the advice of the Health Protection Agency (HPA).
• If OPV is contra-indicated (e.g. immunocompromised patients) give IPV.

• Polio remains endemic in Afghanistan, India, Nigeria and Pakistan; and has been imported elsewhere.
• There is a global polio eradication initiative, launched by the World Health Organisation in 1988. This has eradicated polio from many countries. The strategy remains to eradicate polio altogether through immunisation.