WASHINGTON The rapid introduction of the bivalent
polio vaccine is showing good results so
far in mitigating pocket outbreaks of polio, according to a speaker here
at the 45th Annual National Immunization Conference.
Bruce Aylward, MD, who works with WHOs Global Program for
Vaccines, told an audience at the meeting that since the bivalent polio vaccine
was first introduced into Afghanistan in December 2009, there have been no type
3 cases reported, and only one type 1 case. He said the bivalent polio vaccine
has been shown to induce immunity to types 1 and 3 better than the traditional
trivalent polio vaccine.
Areas that had higher case reports are now reaching higher
immunization numbers, and other countries are now
showing very few or no actual cases, Aylward said. As an example, he said
98% of Indias population has been vaccinated against polio, which
was thought to be impossible 10 years ago.
Aylward credited world health officials and leaders of countries such as
India in being proactive in getting children immunized.
In 1988, the World Health Assembly (WHA), during the annual meeting of
WHO, voted to launch a global goal to eradicate polio. Before 1988, wild
poliovirus (WPV) was endemic in more than 125 countries on five continents,
paralyzing more than 350,000 children per year, or approximately 1,000 children
per day. Since 1988, as a result of an alliance, titled the Global Polio
Eradication Initiative (GPEI), more than 2 billion children have been
vaccinated against polio because of the cooperation of more than 200 countries
and 20 million volunteers, and an international investment of more than $6
GPEI uses a four-pronged polio eradication strategy, which includes: 1)
achieve high infant immunization rates with four doses of oral polio vaccine
containing all three serotypes in the first year of life; 2) conduct mass
immunization campaigns, vaccinating all children aged younger than 5 years not
reached by the health system (these campaigns are known as supplemental
immunization activities); 3) implement a widespread surveillance network to
detect all polio cases and circulating WPV; and 4) conduct targeted
supplemental immunization activities in communities or areas with continuing
polio transmission, known as mop-up campaigns.
By 2007, transmission of WPVs had been interrupted, at least
transiently, in all but four countries (Nigeria, India, Pakistan and
Afghanistan, the endemic countries); polio cases had been reduced to fewer than
2,000 per year; and one of the three serotypes of WPV, type 2, had been
eradicated, according to Aylward.
He told meeting attendees to continue advocacy for immunization
programs, both domestically and in the developing world, because funding
immunization programs is key.
Aylward B. #25627. Presented at: The 45th Annual National Immunization
Conference; March 28-31, 2011; Washington, D.C.
Disclosure: Dr. Aylward reports no relevant financial
Although polio vaccination has been available for decades and tremendous
achievements on the way towards eradication of polio have been achieved, polio
vaccination is still one of the most important tasks worldwide. One of three
serotypes of wild polio viruses, type 2, has been eradicated, therefore
introduction of bivalent polio vaccine, containing type 1 and 3, might be
preferable because of better immunogenicity and compliance. As there is no type
2 circulation anywhere in the world since 1999, exclusion of this type from
polio vaccine might be important also in eliminating even theoretical risk of
resurgence of this type of polio virus.
Vytautas Usonis, MD, PhD
Infectious Diseases in Children Editorial Board member
Disclosure: Dr. Usonis reports no relevant financial disclosure.