Title: What is OPV?
Course: Level 3 - Immunization > Section: Antiviral vaccines

Oral polio vaccine (OPV) gives protection against the three types (types 1, 2 and 3) of viruses that cause poliomyelitis or polio which lead to crippling disease of the brain and spinal cord called acute flaccid paralysis. OPV is a light red or light yellow liquid supplied in vials which either have droppers as caps, or they come with separate glass droppers. All OPV vials provided by WHO/UNICEF have had a vaccine vial monitor (VVM) attached.

The VVM shows the health worker whether the OPV in the vial has been damaged by heat. Note that the vaccine used for routine immunisations in the EPI is not the only type of OPV available. Other types may be issued to control outbreaks of polio if they occur, but are not used for routine protection of infants; after the supplementary immunisation campaign, these vaccines should be returned to the central store.

Storage, Dose, Schedule and Contraindications of OPV

OPV storage is the same as like other vaccines that are between +2°C and +8°C; it is easily damaged by heat. OPV is not harmed by freezing or by freezing and thawing multiple times. The number of doses are four, each of them are two drops. OPV should be given at birth, 6 weeks, 10 weeks and 14 weeks of age. The interval between all doses must be at least four weeks.

The birth dose is known as OPV0; the subsequent doses are referred to as OPV1 (at 6 weeks), OPV2 (at 10 weeks), and OPV3 (at 14 weeks). Don't give OPV0 (the birth dose) to an infant who is more than 14 days old. If this dose has not been provided by 14 days, miss this dose and wait until the child is six weeks old and then give OPV1. You should also give the first doses of the other routine EPI vaccines, including PCV10, at six weeks.

The remaining doses should be given as scheduled at 10 and 14 weeks. If a child spits out the vaccine drops, or vomits immediately after a dose of OPV, it is quite safe to repeat the dose. You should still give the scheduled dose even if a child has diarrhoea at the time; give OPV as usual, but administer an extra (fifth) dose at least four weeks after he or she has received the final dose on the schedule. 99% of those who are vaccinated with four doses of OPV are protected from polio for life, but during the campaigns, children are often given additional boosters of OPV to ensure high herd immunity (see table 3.1 below).

Table 3.1. Summary of OPV

Characteristics | Disruptions
Vaccine type | Live-attenuated antiviral vaccine
Amount(dose) given | Two drops
Route of administration | Into the mouth (Oral)
Number of doses | four (OPV0, OPV1,OPV2 and OPV3)
Schedule | At birth, 6, 10 and 14 weeks of age together with other vaccines
Booster(additional) dose | If the child spits or vomits after OPV, repeat the dose immediately; if the child has diarrhea, give a fifth dose at least 4 weeks after the scheduled fourth dose
Storage | Store between +2°C and +8°C. Never freeze. Vaccine storage is described in Study Session 4
Contra-indications | None
Adverse effect | Very rarely AFP; refer immediately to a health centre
Special precautions | None