Recommendations of the Immunization Practices Advisory Committee Poliomyelitis Prevention: Enhanced-Potency Inactivated Poliomyelitis Vaccine -- Supplementary Statement
The supplementary statement provides information on and recommendations for the use of inactivated poliovirus vaccine (IPV) of enhanced potency.* The Immunization Practices Advisory Committee (ACIP) believes that, in the United States, polio immunization should rely primarily on oral poliovirus vaccine (OPV), with selected use of enhanced-potency IPV as specified in this document. However, this subject should be reviewed on a continuing basis, and an extensive review of polio vaccines and potential vaccine policies will take place during 1988. General recommendations on poliomyelitis prevention, including the use of and schedules for OPV, are found in the current ACIP recommendations (1).
Conventional IPV. IPV was introduced in the United States in 1955 and was used widely until OPV became available during the period 1961-1964. Thereafter, the use of IPV rapidly declined to a level of less than 1% of all polio vaccine distributed annually in the United States.
In recent U.S. studies, three doses of IPV administered in the first year of life produced antibodies to poliovirus serotypes 1, 2, and 3 in 87%, 97%, and 95% of recipients, respectively. More than 99% of children completing the four-dose primary series by 18 months of age produced antibodies to all three serotypes (2).
Enhanced-Potency IPV. A method of producing a more potent IPV with greater antigenic content was developed in 1978 and led to the newly licensed IPV, which is produced in human diploid cells (3). Results of studies from several countries have indicated that a reduced number of doses of IPV produced with this technique can immunize children satisfactorily (4-6). A clinical trial of two preparations of enhanced-potency IPV was completed in the United States in 1984 (7). Children received three doses of one of the enhanced-potency IPVs at 2, 4, and 18 months of age. In spite of the presence of maternal antibodies in the majority of the infants at the time of the first dose, 99%-100% of the children were seropositive for all three poliovirus types at 6 months of age (2 months after their second dose). The percentage of seropositive children did not rise or fall significantly during the 14-month period following the second dose, a result that confirms that seroconversion had occurred in almost all children. Furthermore, geometric mean titers increased 5- to 10-fold following both the second and third doses. Conclusive studies are not yet available concerning antibody persistence following three doses of the enhanced-potency IPV to be made available in the United States. However, unpublished studies of an IPV with lower antigen content have shown 100% seropositivity 5 years after the third dose (2).
The effect of enhanced-potency IPV on the circulation of poliovirus in a community has not yet been determined, but it is likely to be at least as good as that seen with conventional IPV. In a recent study of poliovirus excretion following type 1 vaccine- virus challenge after the third dose of enhanced-potency IPV, the decrease in excretion was at least as great as that after conventional IPV, but still significantly less than that found after three doses of OPV (8).
Indications. Persons with a congenital immune deficiency disease, such as agammmaglobulinemia; an acquired immune deficiency disease, such as acquired immunodeficiency syndrome (AIDS); or an altered immune status as a result of other diseases or immunosuppressive therapy are at increased risk for paralysis associated with OPV. Therefore, if polio immunization is indicated, these persons and their household members and other close contacts should receive IPV rather than OPV. Although a protective immune response following receipt of enhanced-potency IPV cannot be assured, some protection may be provided to the immunocompromised patient. Available data on children previously diagnosed with asymptomatic human immunodeficiency virus (HIV) infection do not suggest that they are at increased risk of adverse consequences from OPV. However, for such persons, use of IPV rather than OPV is prudent since family members may be immunocompromised because of AIDS or HIV infection and may be at increased risk for paralysis from contact with an OPV virus.
Routine primary poliovirus vaccination of adults (generally those 18 years of age or older) residing in the United States is not recommended. Adults at increased risk of exposure to either vaccine or wild poliovirus (1) should receive polio vaccination in accordance with the schedule prescribed on page 797.
In households where polio vaccine is to be administered to immunologically normal children, ACIP recommends giving OPV regardless of the poliovirus-vaccine status of adult household contacts (1). The overall risk of vaccine-associated paralytic disease in immunologically normal contacts of OPV recipients is one case per 5.5 million doses of OPV distributed (9). As an alternative, adult contacts can first complete their primary series of polio vaccine as detailed in the schedule below, if there is strong assurance that subsequent immunization of the child will not be jeopardized or unduly delayed.
Schedules. The primary series for enhanced-potency IPV consists of three 0.5-mL doses administered subcutaneously. The interval between the first two doses should be at least 4 weeks, but preferably 8 weeks. The third dose should follow in at least 6 months, but preferably nearer to 12 months. A primary series can be started as early as 6 weeks of age, but preferably at 2 months of age. Although studies have not been conducted, young children should receive the third dose along with diphtheria, tetanus, pertussis vaccine (DTP) and measles, mumps, rubella vaccine (MMR) at 15 months of age, if possible.
A primary series of polio vaccine usually consists of enhanced-potency IPV alone or OPV alone. However, a combination of both vaccines totalling three doses and separated by appropriate intervals constitutes a primary series. If enhanced-potency IPV is administered to persons with a previously incomplete series of conventional IPV, a final total of four doses of polio vaccine is necessary for a primary series.
All children who received a primary series of enhanced-potency IPV or of a combination of polio vaccines should be given a booster dose before entering school, unless the final dose of the primary series was administered on or after the fourth birthday. The need for routinely administering additional doses is unknown at this time.
For unvaccinated adults at increased risk of exposure to poliovirus, a primary series of enhanced-potency IPV is recommended. While the responses of adults to a primary series have not been studied, the recommended schedule for adults is two doses given at a 1- to 2-month interval and a third dose given 6 to 12 months later. If less than 3 months but more than 2 months are available before protection is needed, three doses of enhanced-potency IPV should be given at least 1 month apart. Likewise, if only 1 to 2 months are available, two doses of enhanced-potency IPV should be given at least 1 month apart. If less than 1 month is available, a single dose of either OPV or enhanced-potency IPV is recommended.
Adults who are at increased risk of exposure and have had 1) at least one dose of OPV, 2) fewer than three doses of conventional IPV, or 3) a combination of conventional IPV and OPV totalling fewer than three doses should receive at least one dose of OPV or enhanced-potency IPV. Additional doses needed to complete a primary series should be given if time permits.
Adults who are at increased risk of exposure and who have previously completed a primary series with any one or combination of polio vaccines can be given a dose of OPV or enhanced-potency IPV.
Side Effects and Adverse Reactions. Available data indicate that the rate of adverse reactions in the kidney cells of monkeys receiving enhanced-potency IPV are low and that the reactions are not different from those following administration of a placebo. The recently licensed human diploid cell-derived vaccine was not compared to a placebo. Rates of local adverse events following its use are similar to rates found in controlled studies using vaccine derived from the kidney cells of monkeys. There is no evidence that conventional IPV causes any serious side effects. Consequently, serious side effects are not expected to occur with enhanced-potency IPV. This conclusion can be confirmed only with postmarketing surveillance. Parents of children receiving the vaccine, older vaccine recipients, and health-care providers are encouraged to report all adverse events occurring within 4 weeks of receipt of enhanced-potency IPV to the manufacturer and to local or state health departments. The information will be forwarded to the appropriate federal agency.**
Precautions and Contraindications. Vaccine administration should not be postponed because of minor illnesses, such as mild upper-respiratory infections. Generally, however, persons with severe febrile illnesses should not be vaccinated until they have recovered.
The enhanced-potency IPV may contain trace amounts of streptomycin and neomycin. Persons who have had anaphylactic reactions to topically or systemically administered streptomycin and neomycin should not receive enhanced-potency IPV.
There is no convincing evidence documenting adverse effects of conventional IPV on the pregnant woman or developing fetus. Data on adverse events following use of enhanced-potency IPV are not available. On theoretical grounds, it is prudent to avoid vaccinating pregnant women. However, if a pregnant woman needs immediate protection against poliomyelitis, OPV is recommended.
* Poliovirus Vaccine Inactivated, which is manufactured by Connaught Laboratories Ltd., will be distributed by Connaught Laboratories Inc. beginning in March 1988.
** Center for Biologics Evaluation and Research, Food and Drug Administration, or the Centers for Disease Control.
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