[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
6229: Polio scare prompts call for more vaccinations (fwd)
From: Greg Chamberlain <GregChamberlain@compuserve.com>
PORT OF SPAIN, (Dec. 13) IPS - Caribbean countries have been urged to beef
up their immunization process in the wake of an outbreak of poliomyelitis
in the Dominican Republic and Haiti.
The outbreak is causing serious concerns in the Western hemisphere,
where there has not been a case of the disease since 1991.
"In essence, the countries have to ensure that immunization remains
extremely high. The rest of the Caribbean will have to ensure that their
surveillance system is sensitive, up to date and functioning very well,"
says Dr. Beryl Irons, the medical epidemiologist and technical adviser to
member states of the Caribbean Epidemiology Center (CAREC).
The last case of poliomyelitis in the Caribbean was reported in 1982 in
Jamaica, while in the Americas, the last recorded case was in 1991.
The Pan American Health Organization (PAHO),which in 1985 launched its
drive to eradicate polio from the Americas says it has 16 epidemiologists
supporting Haiti and the Dominican Republic efforts to vaccinate its
A mass vaccination campaign with oral poliovirus vaccine (OPV) has
already started in the Dominican Republic, initially covering the three
provinces of La Vega, Santiago and Mons Nouel. The campaign will be
extended to the rest of the country at a later stage.
In the case of Haiti, three nationwide vaccination rounds with OPV are
planned for January, February and March, according to an official PAHO
The virus identified in the two affected countries is reported to be an
unusual derivative of the Sabin type 1 oral poliovirus vaccine, says PAHO.
Since July 12, a total of three laboratory- confirmed cases have been
identified. An additional 16 people with acute flaccid paralysis (AFP) are
now being treated in the Dominican Republic.
A single laboratory-confirmed case in Haiti was due to the derived type
1 virus and was located in the town of Nan Citron, with paralysis onset on
The virus was first isolated at the Poliovirus Laboratory at CAREC and
subsequently characterized at the Centers for Disease Control and
Prevention (CDC) in the United States. It is unusual because it is derived
from OPV, has about 97 percent genetic similarity to the parental OPV
strain and appears to have assumed the characteristics of wild polio virus
type 1, both in terms of neurovirulence and transmissibility.
PAHO said the difference in "nucleotide sequence suggests the virus has
been either replicating for a prolonged period in an immune deficient
individual, or circulating for as long as two years in an area where
vaccination coverage is very low."
The health organization said that a similar virus to strain reported in
Haiti and the Dominican Republic had been documented in only one other
setting -- Egypt -- over the 10-year period from 1983 to 1993.
PAHO said the virus was associated with more than 30 reported cases of
"In this instance, vaccination coverage was very low in the affected
areas and circulation of a vaccine-derived poliovirus was terminated
rapidly once OPV vaccination coverage increased," it said.
But PAHO's director of Vaccines and Immunization Dr. Ciro de Quadros
says that an intensive investigation failed to turn up any other cases in
the affected Caribbean countries.
"All the cases were either unvaccinated or had not had their complete
doses of polio vaccine," he said.
But he noted that the "current outbreak is a powerful reminder that even
polio-free areas need to maintain high coverage with polio vaccine until
polio eradication has been achieved."
PAHO said the essential factor for controlling OPV-derived viruses is
the same as that required to control wild poliovirus circulation: high
"No evidence for circulation of OPV-derived virus has ever been found in
any area with high coverage," Dr. de Quadros said.
Dr. Irons said the outbreak in the two Caribbean states was a reflection
of the immunization status in those countries, where coverage is about 80
Dr. Irons said the Port of Spain-based CAREC, which serves the
English-speaking Caribbean and Suriname, was not advocating a ban on travel
to countries where the virus had been detected, noting "that is never a
"We are not advocating a ban on travel, what we say and we tell all
member governments is that they have to ensure that travellers are
adequately immunized," she said.
The PAHO statement warned travellers to the Dominican Republic and Haiti
"who are not adequately immunized" that they "must be considered at risk of
acquiring poliomyelitis and should make certain they are fully immunized
"Those countries using OPV for routine immunization recommend at least
three-dose primary vaccination series," it said.