Highlights From MMWR: CDC Reports on Imported Polio Case and More

Yael Waknine

February 03, 2006

Feb. 3, 2006 — The Centers for Disease Control and Prevention (CDC) reported in the February 3 issue of the Morbidity and Mortality Weekly Report on a case that highlights the previously unknown risk for vaccine-associated paralytic poliomyelitis among unvaccinated individuals traveling abroad; the low rate of annual influenza vaccination for children aged 6 to 23 months, and an increase in the rate of midwife-attended births.

CDC Case Report: Imported Vaccine-Associated Paralytic Poliomyelitis

The CDC has reported on a case that highlights the previously unrecognized risk for paralytic polio among unvaccinated individuals exposed to attenuated oral polio (OPV) during travel to abroad.

In 2005, an Arizona woman aged 22 years contracted paralytic polio while residing with a host family and traveling in Central and South America on a university-sponsored study-abroad program. She was hospitalized locally for acute leg weakness, and then airlifted to Phoenix for further evaluation.

The patient had never been vaccinated with either OPV or inactivated polio vaccine (IPV) due to religious exemption; any known exposure was limited to contact with the host family's infant grandchild, who had received an initial dose of OPV four days after her arrival.

Although the patient was initially treated for an acute peripheral demyelinating process, clinical history, physical findings, and laboratory studies were typical for paralytic polio and inconsistent with Guillain-Barre syndrome, transverse myelitis, or other forms of acute flaccid paralysis.

The CDC notes that the change from an OPV-only to a sequential IPV/OPV vaccination schedule in 1997, followed by implementation of an all-IPV schedule in 2000 has resulted in elimination of vaccine-associated paralytic polio (VAPP) in the US. According to CDC, the most recent case of VAPP prior to this report occurred in 1999.

Because of the minimal risk for poliovirus exposure and the high rate of immunity conferred by routine childhood vaccinations, routine vaccination of adults residing in the US is only recommended for those at increased risk for exposure.

Previously OPV- or IPV-vaccinated adults traveling to areas where polio is still epidemic or endemic should receive a dose of IPV prior to departure; data suggest that only a single lifetime booster dose of IPV is needed.

Adults who are unvaccinated, incompletely vaccinated, or whose vaccination status is unknown should receive 2 doses of IPV separated by an interval of 4 to 8 weeks, followed by a third dose 6 to 12 month later. In the presence of time constraints, the intervals may be reduced to 4 weeks for maximized coverage.

The CDC advises that international travelers contact travel medicine providers at least 4 to 6 weeks prior to departure in order to obtain vaccinations and prophylactic medications. Providers should assess the need for itinerary-specific vaccines and ensure that travelers are current with routine vaccinations, including IPV.

Information on vaccination requirements for international travelers is available from the CDC publication, Health Information for International Travel, 2005-2006, online at http://www.cdc.gov/travel/yb/index.htm.

ACIP Guidelines Lead to Increased Influenza Vaccination Rates for Children

During the second influenza season for which the Advisory Committee on Immunization Practices (ACIP) encouraged annual vaccination of children aged 6 to 23 months, vaccination rates increased in this population but remained low, according to an analysis of provider data from the 2004 National Immunization Survey (NIS).

The findings revealed that during the 2003/2004 influenza season, 17.5% of children aged 6 to 23 months received one or more doses of influenza vaccine, and 8.4% were fully vaccinated (2 doses). Corresponding rate estimates for the previous 2002/2003 season were 7.4% and 4.4%, respectively.

According to CDC, these low rates are of concern because study data suggest that single doses of the 2003 vaccine were not statistically linked with a reduction in the risk for medically attended influenza-like illness (ILI) or pneumonia and influenza (P&I) in this population. Corresponding rates for fully vaccinated children were 25% and 49%, respectively.

Influenza vaccination coverage was also found to vary substantially among states and selected urban areas. The rate of children receiving 1 or more doses of influenza vaccine ranged from 5.7% in Miami-Dade County, Florida, to 47.6% in Rhode Island.

The CDC notes that the rise in coverage may reflect increased provider implementation (expansion of the Vaccines for Children program) and parental awareness of the ACIP encouragement, which was publicized by the media when an early peak in influenza activity was linked to the deaths of 153 children.

However, the nature of the encouragement (vs recommendation) and variations in local outbreak severity, perception of associated risk, and provider access may have contributed to the wide variation observed in influenza vaccination rates.

For the 2004/2005 season, ACIP strengthened its encouragement to a recommendation that included vaccination of children aged 6 month to 18 years with certain high-risk medical conditions, are on chronic aspirin therapy, or who have household contact with persons at high risk for influenza-related complications.

As a result, vaccination rates for children appear to have increased despite an overall vaccine shortage during the 2004/2005 influenza season. Parent-reported data from the Behavior Risk Factor Surveillance System (BRFSS) indicated that 48.4% of children aged 6 to 23 month received at least 1 dose of vaccine, and an analysis of immunization registry and enrollment data from one large health maintenance organization (HMO) revealed a coverage rate of 57.4% for this population.

According to CDC, full implementation of the new recommendations is needed to reduce the number of preventable influenza-based hospitalizations among young children. Complete vaccination recommendations, and updates on the 2005/006 influenza season and vaccine supply are available online at http://www.cdc.gov/flu.

Rate of Midwife-Attended Births Increasing in the US

The percentage of births attended by midwives in the US has more than doubled over the last 13 years, according to an analysis of data from the National Vital Statistics System.

In 2003, approximately 8.0% of births were attended by midwives, compared with 3.9% in 1990. In 6 states (Alaska, Georgia, New Hampshire, New Mexico, Oregon, and Vermont), rates were at least twice as high as the national rate.

MMWR.2005;55;93-120.

Reviewed by Gary D. Vogin, MD

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