Needle-Free Polio Vaccination House to House in Sokoto, Nigeria, Reached 87% of Children

A pilot in one ward of Sokoto State, Nigeria, in November 2022 showed that an injected polio vaccine can be given house to house with needle-free jet injectors, and reach 87% of young children.

Why it was tried

After wild poliovirus type 2 was declared eradicated in 2015, the type 2 component of the Sabin oral polio vaccine (OPV) was withdrawn worldwide in 2016, switching from trivalent to bivalent OPV, to cut the rare risk of paralysis caused by the vaccine itself. The Global Polio Eradication Initiative asked OPV-using countries to add at least one dose of inactivated polio vaccine (IPV) to routine immunisation. IPV protects against paralysis from all three types but cannot spread between people or cause paralysis.

Oral vaccine, especially where coverage is low, carries a small risk of vaccine-derived poliovirus emerging. As children born after the switch built up without type 2 immunity, circulating vaccine-derived poliovirus type 2 (cVDPV2) emerged, and when response campaigns were not good enough, new outbreaks followed. In 2021 a more genetically stable novel OPV2 (nOPV2), less likely to regain the ability to paralyse, replaced the older monovalent vaccine, but campaigns still have to reach most children.

A single routine IPV dose at 14 weeks protects about 60% of recipients against paralysis, yet coverage is low in many countries. Many subnational areas of Nigeria, especially in the north, reported IPV coverage below 50% in a 2021 national survey; Sokoto reported 27%, and outbreak transmission there continued despite eight nOPV2 campaigns since March 2021.

Inactivated polio vaccine one-dose coverage by state, Nigeria, 2021 (National Immunization Coverage Survey and Multiple Indicator Cluster Survey). CDC.

The pilot

To stretch scarce vaccine, a fractional dose (fIPV), one fifth of a full dose injected into the skin, can be given twice at least 4 weeks apart in place of one full intramuscular dose. A large fixed-site fIPV campaign in Pakistan reached 85% coverage. The question here was whether it could be done door to door with a needle-free jet injector.

In the ward of Sarkin Adar Gidan Igwai, one fIPV dose was added to an nOPV2 campaign already planned for November 2022, for children aged 3–59 months. Nurses trained on the devices joined the oral-vaccine teams and filled each cartridge from a multidose vial in the home. Most parents (94%) and health staff (93%) preferred the needle-free injection to a needle and syringe.

A follow-up survey of 210 children in 30 settlements, using the World Health Organization's modified cluster method, found that 87% had received the dose.

What next

The pilot shows the approach is workable and can reach high coverage. Stronger routine immunisation, with more sessions, supportive supervision and reliable vaccine supply, will be needed to give the ward's children their second fractional dose, and larger pilots should come before it is used in other low-coverage areas.

Sources

• Biya O, Manu JI, Forbi JC, et al. "Notes from the Field: House-to-House Campaign Administration of Inactivated Poliovirus Vaccine — Sokoto State, Nigeria, November 2022," MMWR. https://www.cdc.gov/mmwr/volumes/72/wr/mm7247a3.htm
• The report discloses that one author owns shares in the maker of the jet injector used.