The last significant outbreak in Canada was in 1978-79, when 11 cases of paralytic

disease occurred in unimmunized contacts of imported cases in religious groups in

Ontario, Alberta and British Columbia. In 1993, 22 asymptomatic cases of imported

wild polio infection were documented in the same religious group in Alberta, and in

1996 a similar case occurred in an asymptomatic child in Ontario. In none of these

instances was spread of the virus seen outside the unimmunized groups, presumably

because of high levels of immunization in the rest of the population.

Since 1980, 12 paralytic cases have been reported in Canada, 11 of which were determined

to be vaccine-associated paralytic poliomyelitis (VAPP). Since 1987, all suspected

cases of paralytic poliomyelitis have been reviewed by a subcommittee of NACI

or, since 1994, the National Working Group on Polio Eradication. The last reported

case caused by a wild poliovirus occurred in 1988 and was found to be due to an

imported strain from the Indian subcontinent. Of the other 11 cases, three have been

classified as "confirmed" vaccine-associated contact cases, five as "possible" vaccineassociated

contact cases, and one as a "confirmed" vaccine- associated recipient case;

the two other cases were not reviewed but occurred in known contacts of OPVvaccinated

children. The last reported case of VAPP occurred in 1995.

Both inactivated (IPV) and live oral (OPV) poliovirus vaccines are licensed for use in

Canada. However, because in the past decade all cases of polio or suspected polio

have been associated with OPV and because importations of wild poliovirus have not

led to transmission to anyone in Canada outside of groups that refuse immunization,

only IPV is recommended for routine use in Canada. For this reason, OPV is not

discussed in detail in this chapter.

Two IPV preparations are licensed, one produced on Vero cells and the other on

human diploid (MRC-5) cells. Both are formalin-inactivated products with enhanced

potency and are significantly more immunogenic than the original IPV. They each

contain the three types of wild poliovirus. Streptomycin, polymyxin B and neomycin

may be present as preservatives. Polio vaccine is available as a single agent or in

combination with diphtheria and tetanus toxoids and/or acellular pertussis vaccine

(DTaP-IPV, Td-IPV).

IPV produces immunity to all three types of poliovirus in over 90% of people following

two doses of vaccine given at least 6 weeks apart, and in close to 100% following

a booster given 6 to 12 months later. The immune response induced in IPV

vaccinees reduces the degree and duration of pharyngeal and fecal excretion of

poliovirus after OPV challenge, as compared with unvaccinated children. However,

IPV produces less mucosal immunity than OPV.

To avoid the risk of VAPP, exclusive use of IPV is recommended in Canada. Use of OPV

alone or sequential use of IPV followed by OPV provides acceptable levels of protection,

but both schedules carry the risk of VAPP in recipients or their contacts and

neither offers any protective advantage to the recipient.

Routine immunization against poliomyelitis for adults living in Canada is not considered

necessary. Most adults are already immune and have a negligible risk of

exposure to wild polioviruses in the Americas.

Primary immunization with poliomyelitis vaccine is recommended only in those who

are unimmunized and are at increased risk of exposure to poliovirus. Such people

include the following:

or vaccine strains of polioviruses;

countries where OPV is used.

Two doses of IPV are recommended 4 to 8 weeks apart, followed by a booster dose 6

to 12 months later. When given combined with DPT (or DTaP), it is acceptable to

give additional doses of IPV 4 to 8 weeks after the second dose and 4 to 6 years after

the third dose for convenience of administration. However, two doses of IPV plus a

booster dose are considered a complete primary series.

For children who began their polio immunization series in a country where OPV is

used, immunization may be completed using IPV; there is no need to re-start the

series. Conversely, children who have been started on an immunization series with

IPV and who move to an area where OPV is used may receive the necessary doses of

OPV to complete their series.

For unimmunized adults at increased risk, primary immunization with IPV is recommended

as two doses given at an interval of 4 to 8 weeks with a further dose

6 months to 1 year later. Additional considerations are as follows:

dose of IPV and the remaining doses later, at the recommended intervals;

receive OPV, there is a very small risk of OPV-associated paralysis to unimmunized

parents or other household contacts. It will generally not be practical for such

people to be fully protected with IPV before the infant is immunized; their risk

may be reduced if they are given one dose of IPV at the same time as the first dose

is given to the infant. Arrangements should be made for the adults to complete

their basic course of immunization.

Incompletely immunized adults at increased risk who have previously received less

than a full primary course of IPV or OPV should receive the remaining dose(s) of

poliovirus vaccine as IPV, regardless of the interval since the last dose.

IPV is injected subcutaneously according to the dose specified in the manufacturer’s

package insert. Combination vaccines must be administered intramuscularly

because of the presence of adsorbed tetanus and diphtheria toxoids.

A need for booster doses of poliovirus vaccine in fully immunized adults has not

been demonstrated. For those believed to be at particularly high risk of exposure to

polio (e.g., military personnel, workers in refugee camps in endemic areas, travellers

to areas where there are epidemics) a single booster dose of IPV (or OPV) might

be considered. However, booster doses of vaccine are not usually necessary and are

not routinely recommended for travellers.

If transmission of paralytic poliomyelitis caused by wild virus occurs in a community,

OPV should be administered to all individuals (including infants) who have not

been completely immunized or whose immunization status is uncertain. OPV is

recommended because it blocks transmission by competing with wild virus in the

bowel. As well, the local (gut) immunity produced by OPV is greater than that

induced by IPV and is more likely to block asymptomatic infection and transmission.

Thus, IPV should not be used for control of outbreaks of poliomyelitis if OPV is

available.

The side effects of currently available IPV are normally limited to minor local reactions.

As with all vaccines, anaphylaxis has been reported rarely.

OPV may cause paralytic disease in recipients and incompletely immunized contacts

at a rate of approximately 1 per 1 million doses distributed. Individuals travelling or

living abroad whose children may be exposed to OPV should be made aware of this

risk.

IPV should not be administered to people who have experienced an anaphylactic

reaction to a previous dose of IPV, streptomycin, polymyxin B or neomycin.

IPV can be given without risk to those who are immunodeficient or immunosuppressed

or to people who will have household or similarly close contact with such people. Less

than optimal protection may be induced in those who are immunocompromised.

IPV is not contraindicated in pregnancy, but its administration should be delayed

until after the first trimester, if possible, to minimize any theoretical risk. If risk of

exposure is imminent, IPV should be given and is always the vaccine of choice except

for outbreak control.

Can J Infect Dis 1992;3:142-3.

J Infect Dis 1997;175(Suppl 1);S4-9.

1990;37:627-47.

1999.

Sabin AB. My last will and testament on rapid elimination and ultimate global eradication of

poliomyelitis and measles. Pediatrics 1992;90:162-9.

FROM THE CANADA IMMUNIZATION GUIDE 6ed