Can a patient started on Inactivated Poliovirus Vaccine (IPV) be shifted to Oral Poliovirus Vaccine (OPV) in certain locations?

Shifting from IPV to OPV in Routine Immunization

Patients started on IPV should NOT be routinely shifted to OPV for completion of the primary vaccination series in the United States and other countries using IPV-only schedules. 1

Current Guideline Recommendations

United States Policy (2000-Present)

• The CDC/ACIP recommends exclusive use of IPV for all routine childhood polio vaccination, with a 4-dose schedule at ages 2,4,6-18 months, and 4-6 years 1, 2
• This policy was implemented specifically to eliminate vaccine-associated paralytic poliomyelitis (VAPP), which occurred at a rate of approximately 1 case per 2.4 million OPV doses distributed 1
• Children who begin vaccination with IPV should complete the entire series with IPV 2

Interchangeability of Vaccines

• IPV and OPV can be used interchangeably to complete a vaccination series when necessary, as both vaccines induce protective antibody levels (>95% seroconversion) after a complete primary series 1
• The minimum intervals between doses remain the same regardless of vaccine type previously received: 4 weeks between doses 1-2 and 2-3, and 6 months between doses 3-4 2

Limited Acceptable Indications for Switching to OPV

The ACIP identifies only three specific circumstances where OPV may be used after IPV initiation 1:

1. Outbreak Control Settings

• OPV is the vaccine of choice for mass vaccination during polio outbreaks, even in populations previously vaccinated with IPV 1
• OPV provides superior intestinal immunity, higher single-dose seroconversion rates, and beneficial secondary spread through vaccine virus shedding 1
• Historical examples include the 1992-93 Netherlands outbreak and 1984-85 Finland outbreak, where countries using IPV routinely switched to OPV for outbreak control 1

2. Imminent Travel to Endemic Areas

• Unvaccinated children traveling in fewer than 4 weeks to polio-endemic areas may receive OPV if IPV is unavailable 1
• This is based on OPV's faster onset of protection after a single dose (approximately 50% develop antibodies to all three serotypes) compared to IPV 1

3. Parental Refusal of Injections

• Children whose parents refuse the recommended number of vaccine injections may receive OPV only for the third or fourth dose 1
• Healthcare providers must discuss the risk of VAPP before administering OPV in this situation 1

Critical Safety Considerations

Absolute Contraindications to OPV Use

OPV should never be given to 1:

• Immunocompromised individuals (immune deficiency diseases, HIV infection, leukemia, lymphoma, generalized malignancy)
• Persons receiving immunosuppressive therapy (corticosteroids, alkylating drugs, antimetabolites, radiation)
• Household contacts of immunocompromised individuals
• Anyone in families with a known history of immunodeficiency until immune status is documented

Why IPV is Preferred

• IPV eliminates the risk of VAPP entirely while maintaining high individual protection 1, 2
• IPV is safe for immunocompromised patients and their contacts 1
• No serious adverse events are associated with IPV use 2

Immunologic Equivalence

• Both IPV and OPV induce protective immunity in >95% of recipients after a complete primary series 1
• Three doses of either vaccine induce protective antibody levels (neutralizing antibody titers >1:8) to all three poliovirus serotypes 1
• Sequential IPV-OPV schedules show little or no difference in protective humoral response compared to IPV-only schedules 3

Common Pitfalls to Avoid

• Do not switch to OPV simply to reduce injection burden unless parents absolutely refuse injections and only for doses 3-4 1
• Do not use OPV in any immunocompromised patient or their household contacts, even if the series was started with IPV 1
• Do not restart the vaccine series regardless of time elapsed between doses or vaccine type changes 2
• Ensure the final dose is given at age ≥4 years regardless of previous vaccine type, as this is critical for long-term immunity 1, 2

Global Context

• While the WHO recommended at least one IPV dose preceding OPV in 2016 for countries still using OPV 3, high-income countries with IPV-only schedules should not revert to OPV 1
• OPV remains essential for global polio eradication efforts in endemic countries but is not appropriate for routine use in polio-free regions 1, 4