3b.9 Why are we still vaccinating for polio, then?
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This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax lynng@alsirat.com with numerous contributions by others.
3b.9 Why are we still vaccinating for polio, then?
The AAP and ACIP continue to recommend vaccination for polio for
several reasons. First, the risk of the disease is much higher than
the risk of the vaccine. Second, though there is no wild polio in the
US *now*, with high levels of vaccination, there is still polio
elsewhere in the world. 148,000 cases were reported to WHO in
1990. China reported 5,065 cases. The USSR reported 337 cases. India
reported 7,340. (Hull and Ward) There have been several outbreaks of
polio in countries 2 or more years after the last reported case of
polio. Importation from polio endemic countries has led to outbreaks
in Oman (1988-89 and 1993), Jordan (1991-92), Malaysia (1992), and the
Netherlands (1992-93) (MMWR, reported in HICNet Medical News on 15
August 1994). Wild poliovirus type 3 was isolated during
January-February 1993 among members of a religious community objecting
to vaccination in Canada (although no actual cases of parlytic polio
occurred in Canada at this time). There is a concern that if levels
of vaccination were reduced in the US, polio could be reintroduced,
and we could see polio epidemics here again.
Encouraged by the worldwide elimination of smallpox, WHO, in 1988, set
a goal of eradicating polio from the world by 2000. Since then, the
number of cases in the world has declined dramatically (29,916 in 1989
and 16,435 in 1990), and the number of countries reporting 0 cases has
increased (74 countries in 1985 and 116 countries in 1990). As of
1993, the number of cases worldwide has falled to 9714, and nearly 70
percent of all countries reported no cases. (Progress toward global
eradication of poliomyelitis, 1988-1993. MMWR 1994 Jul 15;
43:499-503. Summarized in Journal Watch Summaries for July 22, 1994.)
As of 1999, WHO reports still further progress, "In 1988, virus
circulated widely on all continents except Australia. By 1998, the
Americas were polio-free (certification of eradication in 1994),
transmission has been interrupted in the Western Pacific Region of
WHO, including China, and in the European Region, except for a small
focus in south-east Turkey. As shown below, only three major foci of
transmission remain: South Asia (Afghanistan, Pakistan, India), West
Africa (mainly Nigeria) and Central Africa (mainly Democratic Republic
of Congo)." So another factor in the decision to continue vaccinating
for polio is the hope that it can be eliminated for good.
After much debate, the US has switched to IPV instead of OPV (IPV
being less effective, but lower in side effects). The decision at
first was to continue with OPV because it has been so successful, the
rate of side effects is still considered very low, and because of
various advantages in producing immunity (see above). According to the
1993 PDR, "The choice of OPV as the preferred poliovirus vaccine for
primary administration to children in the United States has been made
by the ACIP, the Committee on Infectious Diseases of the American
Academy of Pediatrics, and a special expert committee of the Institute
of Medicine, National Academy of Sciences." In 1995, though, that
decision was changed, and the injected vaccine became recommended for
the first two polio shots. As progress toward worldwide polio
eradication continued, and as the change in the vaccination schedule
(from an oral to an injected form) did not result in any decline in
vaccination coverage, ACIP and AAP are now recommending IPV for all
shots.
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