Recommendations for poliovirus vaccination of adults in the above categories depend upon the previous vaccination history and the time available before protection is required.

For unvaccinated adults at increased risk of exposure to poliomyelitis, primary immunization with IPV is recommended. IPV is preferred because the risk of vaccine-associated paralysis following OPV is higher in adults than in children. The recommended schedule is two doses given at a 1- to 2-month interval, and a third dose given 6 to 12 months later.

In some circumstances time will not allow completion of this schedule. If 8 weeks or more are available before protection is needed, three doses of IPV should be given at least 4 weeks apart. If 4-8 weeks are available before protection is needed, two doses of IPV should be given at least 4 weeks apart. If less than 4 weeks are available before protection is needed, a single dose of either OPV or IPV is recommended. In all instances, the remaining doses of vaccine should be given later, at the recommended intervals, if the person remains at increased risk.

Adults who have previously completed a primary course of OPV and who are at increased risk of exposure to poliomyelitis may be given another dose of OPV (if available). These adults are not at increased risk of VAPP. The need for further supplementary doses has not been established. Those adults who previously completed a primary course of IPV and are at increased risk may be given a dose of either IPV or OPV.

Adults who have previously received less than a full primary course of OPV or IPV and who are at increased risk of exposure to poliomyelitis should be given the remaining doses of IPV, regardless of the interval since the last dose and type of vaccine previously received. It is not necessary to restart the series of either vaccine if the schedule has been interrupted.

4. Adverse Reactions Following Vaccination

Minor local reactions (pain, redness) may occur following IPV. No serious adverse reactions to IPV have been documented. Because IPV contains trace amounts of streptomycin, polymyxin B, and neomycin, allergic reactions may occur among persons sensitive to these antibiotics. In rare instances, administration of OPV has been associ-ated with paralysis in healthy recipients and their contacts. No procedures are currently available for identifying persons, other than those with immunodeficiency, who are likely to experience such adverse reactions. Although the risk of vaccine-associated paralysis is minimal, vaccinees (or their parents) and their susceptible, close, personal contacts should be informed of this risk.

5. Vaccine-Associated Paralytic Poliomyelitis (VAPP)

Vaccine-associated paralytic polio (VAPP) is a rare adverse event following live oral poliovirus vaccine. Inactivated poliovirus vaccine does not contain live virus, so it cannot cause VAPP. The mechanism of VAPP is believed to be a mutation, or reversion, of the vaccine virus to a more neurotropic form. These mutated viruses are called revertants. Reversion is believed to occur in almost all vaccine recipients, but it only rarely results in paralytic disease. The paralysis that results is identical to that caused by wild virus, and may be permanent.

VAPP is more likely to occur in persons >18 years of age than in children, and is much more likely to occur in immunodeficient children than in those who are immuno-logically normal. Compared with immunocompetent children, the risk of VAPP is almost 7000 times higher for persons with certain types of immunodeficiencies, particularly B lymphocyte disorders (e.g., agammaglobulinemia and hypogammaglobulinemia) which reduce the synthesis of immune globulins. There is no procedure available for identifying persons at risk of paralytic disease, except excluding older persons and screening for immunodeficiency. VAPP is usually permanent.

From 1980 through 1998, 152 persons with paralytic polio were reported in the United States; 144 (95%) of these cases were VAPP, and the remaining 8 persons acquired documented or presumed wild virus polio outside the U.S. Of the 144 VAPP cases reported during 1980-1998, 59 (41%) occurred in healthy vaccine recipients (average age 3 months). Forty-four (31%) occurred in healthy contacts of vaccine recipients (average age 26 years), and 7 (5%) were community acquired (i.e., vaccine virus recovered but there was no known contact with a vaccine recipient). Thirty-four (24%) of VAPP cases occurred in persons with immunologic abnormalities (27 in vaccine recipients and 7 in contacts of vaccine recipients). None of the vaccine recipients were known to be immunologically abnormal prior to vaccination.

Moderate or severe acute illness is a precaution for both IPV and OPV. However, mild illness, including mild diarrhea, is not a contraindication.

Breast feeding does not interfere with successful immunization against poliomyelitis with IPV or OPV. A dose of IPV may be administered to a child with diarrhea. Minor upper respiratory illnesses with or without fever, mild to moderate local reactions to a previous dose of vaccine, current antimicrobial therapy, and the convalescent phase of an acute illness are not contraindications for vaccina-tion with IPV or OPV.

OPV should not be given to immunodeficient individuals or household contacts of individuals who have immune deficiency diseases, immune depression (due to disease or therapy), or if there is suspected familial immune deficiency. IPV may be substituted for OPV in these circumstances.

If OPV is inadvertently administered to a household contact of an immunodeficient patient, the patient and the recipient of OPV should avoid close contact for approximately 4-6 weeks after vaccination. If this is not feasible, rigorous hygiene and hand washing after contact with feces (e.g., after diaper changing) and avoidance of contact with saliva (e.g., sharing food or utensils) may be an ac-ceptable, but probably less effective alternative. Maximum excretion of vaccine virus occurs within 4 weeks after oral vaccination.

In general, neither OPV nor IPV should be given to pregnant women unless immediate protection is needed (in which case OPV is the vaccine of choice, if available).

The risk of VAPP is not equal for all OPV doses in the vaccination series. The risk of VAPP is 7 to 21 times higher for the first dose than for any other dose in the OPV series. From 1980 through 1994, 303 million doses of OPV were distributed and 125 cases of VAPP were reported, for an overall risk of VAPP of 1 case per 2.4 million doses. Forty-nine paralytic cases were reported among immunologically normal recipients of OPV from 1980 through 1994. The overall risk to these recipients was one VAPP case per 6.2 million OPV doses. However, 40 (81.6%) of these 49 cases occurred following receipt of the first dose. The risk of VAPP was 1 case per 1.4 million first doses. The risk for all other doses was one per 27.2 million doses. The reason for this difference by dose is not known with certainty, but is probably because the vaccine virus is able to replicate longer in a completely nonimmune infant. This prolonged replication increases the chance of the emergence of a revertant virus that may cause paralysis. The situation is similar for contacts. A nonimmune child may shed virus longer, increasing the chance of exposure of a contact.

6. Contraindications and Precautions to Vaccination

Serious allergic reaction to a vaccine component, or following a prior dose of vaccine, is a contraindication to further doses of that vaccine. Since IPV contains trace amounts of streptomycin, neomycin, and polymyxin B, there is a possibility of allergic reactions in individuals sensitive to these antibiotics. Persons with allergies that are not anaphylactic, such as skin contact sensitivity, may be vaccinated.

Moderate or severe acute illness is a precaution for both IPV and OPV. However, mild illness, including mild diarrhea, is not a contraindication.

Breast feeding does not interfere with successful immuni-zation against poliomyelitis with IPV or OPV. A dose of IPV may be administered to a child with diarrhea. Minor upper respiratory illnesses with or without fever, mild to moderate local reactions to a previous dose of vaccine, current antimicrobial therapy, and the convalescent phase of an acute illness are not contraindications for vaccination with IPV or OPV.

OPV should not be given to immunodeficient individu-als or household contacts of individuals who have immune deficiency diseases, immune depression (due to disease or therapy), or if there is suspected familial im-mune deficiency. IPV may be substituted for OPV in these circumstances.

If OPV is inadvertently administered to a household contact of an immunodeficient patient, the patient and the recipient of OPV should avoid close contact for approximately 4-6 weeks after vaccination. If this is not feasible, rigorous hygiene and hand washing after contact with feces (e.g., after diaper changing) and avoidance of contact with saliva (e.g., sharing food or utensils) may be an ac-ceptable, but probably less effective alternative. Maxi-mum excretion of vaccine virus occurs within 4 weeks after oral vaccination.

In general, neither OPV nor IPV should be given to pregnant women unless immediate protection is needed (in which case OPV is the vaccine of choice, if available).