Bivalent polio vaccine may be making a dent on pocket outbreaks

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 WHO’s 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 India’s 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 billion.

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 disclosures.

Vytautas Usonis

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.

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