Oral Polio Vaccine

WHO Global Polio Eradication Initiative: routine childhood immunization in endemic and at-risk countries (sequential IPV-OPV schedule or OPV-only in some settings). Supplementary immunization activities (SIAs) and mass campaigns in outbreak response. nOPV2: specifically for outbreak response to circulating vaccine-derived poliovirus type 2 (cVDPV2). Some countries require proof of OPV/IPV vaccination for travelers departing from endemic/outbreak areas under International Health Regulations (IHR).

Severe allergic reaction to previous dose or any component (including streptomycin, neomycin, polymyxin B). Immunocompromised individuals: primary immunodeficiency, symptomatic HIV, ongoing immunosuppressive therapy — use IPV instead (risk of vaccine-associated paralytic poliomyelitis, VAPP). Household contacts of immunocompromised persons should receive IPV, not OPV. Acute vomiting or diarrhea (defer — may reduce efficacy).

Generally very well tolerated. Common: transient mild diarrhea, low-grade fever. Rare but critical: Vaccine-Associated Paralytic Poliomyelitis (VAPP) — approximately 1 per 2.7 million first doses (predominantly in immunodeficient individuals). Risk highest with first dose in unprimed recipients. Circulating Vaccine-Derived Poliovirus (cVDPV): reverted Sabin strains can circulate in under-immunized populations and cause outbreaks — primary reason for global OPV-to-IPV transition. nOPV2: genetically stabilized to reduce reversion risk.

bOPV: 2 drops oral per dose. Standard WHO schedule: birth dose (OPV0) + 3 doses at 6, 10, 14 weeks + ≥1 IPV dose at 14 weeks. Many countries now use sequential schedule: 1–2 IPV doses followed by OPV doses. Mass campaigns: single dose per round. nOPV2: 2 drops oral, used in targeted outbreak response campaigns. Store at -20°C (long-term) or +2°C to +8°C (up to 6 months). Protect from light.

bOPV: ≥90% seroconversion for types 1 and 3 after 3 doses. Superior mucosal immunity compared to IPV — key for interrupting transmission in endemic settings. nOPV2: non-inferior immunogenicity to mOPV2 with significantly reduced genetic reversion risk (10-fold reduction in neurovirulence markers). Global impact: OPV campaigns have reduced wild poliovirus cases by >99.9% since 1988 (350,000 → <100 annually).

Can be given simultaneously with all routine childhood vaccines. Breastfeeding does not reduce efficacy (previous concern disproven). Antibiotics and antimalarials do not interfere. Oral typhoid vaccine (Ty21a): no interference, but space ≥1 day if giving both oral vaccines for practical reasons.

Pregnancy: OPV (live attenuated) is generally not recommended during pregnancy in countries using IPV. However, the WHO states that OPV may be given to pregnant women during polio outbreaks or when traveling to endemic/epidemic areas, as the risk of polio disease outweighs theoretical vaccine risks. Decades of OPV use have not demonstrated adverse effects on the fetus. In endemic countries, OPV is part of routine supplementary immunization activities and is given regardless of pregnancy status.

Breastfeeding: OPV is compatible with breastfeeding. While maternal antibodies in breast milk may slightly reduce the infant's immune response to OPV, this effect is not considered clinically significant. The WHO recommends administering OPV to infants regardless of breastfeeding status. Breastfeeding women can receive OPV if indicated (e.g., during outbreak response campaigns). No interruption of breastfeeding is necessary for either the mother or the infant receiving OPV.

Pediatric use: OPV is a mainstay of the Global Polio Eradication Initiative. The WHO recommends a birth dose of OPV followed by doses at 6, 10, and 14 weeks, often with at least one dose of IPV. OPV provides both individual protection and community immunity through secondary spread of vaccine virus. The risk of vaccine-associated paralytic poliomyelitis (VAPP) is approximately 1 per 2.7 million first doses. Countries that have eliminated wild poliovirus have switched to IPV-only schedules. Novel OPV type 2 (nOPV2) has been developed with reduced risk of genetic reversion.

Older adults (≥65 years): OPV is not routinely used in older adults in countries using IPV. If an unvaccinated older adult is traveling to a polio-endemic area, IPV is the preferred vaccine. Adults who completed a primary series may receive a single lifetime IPV booster before travel. OPV should be avoided in immunocompromised elderly individuals due to the risk of vaccine-associated paralytic poliomyelitis (VAPP), which is higher in immunodeficient persons.

NEVER administer to immunocompromised individuals or their close contacts — use IPV exclusively. Vaccine virus shedding in stool occurs for 4–6 weeks post-vaccination — relevant in households with immunocompromised members. OPV is being phased out globally as part of the Polio Endgame Strategy 2019–2023 (extended). All countries should introduce ≥1 dose of IPV into routine schedules. nOPV2: available only through WHO/UNICEF for authorized outbreak response, requires monitoring.