According to MHO Two Vaccines Work Better Than One

The resolution of the debate that for six decades has disputed the convenience of one or another vaccine for the prevention of poliomyelitis is in the administration of both, according to a study published on Thursday in the journal Science.

The authors, led by Hamid Jafari of the World Health Organization (WHO), recalled in a teleconference MHO the “fierce dispute” that has existed since the 1950s about the use of the inactivated polio virus produced by Salk or the attenuated live virus. of polio offered by Sabin.

“The debate continued even after the goal of global eradication of polio was established in 1988 for which the attenuated virus vaccine was chosen,” Jafari said.

The study was conducted with children in India who had already been vaccinated with the live virus, and shows that a single dose of the inactivated vaccine stimulates immunity more effectively than a “booster” of the vaccine with the live virus.

Global vaccination with the live virus meant that the number of countries where polio was endemic rose from 125 in 1988 to 3 in 2013 and the incidence decreased by 99 percent, the researchers said.

Transmission of polio virus type 2 was stopped globally in 1999 and the last case of polio virus type 3 was detected in November 2012.

“However, in parts of three countries, Afghanistan, Nigeria and Pakistan, we continue to report cases of polio virus type 1 and the export of this virus causes outbreaks ,” the study said.

Jafari explained that live attenuated virus offers some advantages such as superior mucous membrane immunity, ease of administration that does not require a needle and injection and a lower price, but “the vaccine has its limitations”

Among them are that it generates a low level of immunity in some tropical countries and incomplete intestinal immunity that fades rapidly. “To interrupt the transmission of the active virus, the attenuated virus should be administered to a high proportion of children, ” the study said.

The research team conducted a randomized clinical trial in northern India in which nearly 1,000 children received one or the other of the vaccines. After four weeks, all of them were given an additional dose of live attenuated virus.

In children who had first received the dose of inactive virus, the amount of virus debris in the stool generated by the attenuated active virus decreased by 39 to 76 percent, the article says.

In contrast, in children who had already received a dose of attenuated live virus, the decrease “was not significant in the age group of six months to five years, although it was 41 to 52 percent among children ten years of age. age, “he added.

This means that these children were less infectious to others, a key aspect to stop the spread of the virus. Also, the immunity of the intestinal mucosa was strengthened in the group that had received the inactive virus and that left them more protected against the infection of the polio virus.

“Thus, more than 25 years after the World Health Assembly passed a resolution for the eradication of polio, the response to the vaccine controversy is apparent: both should be used,” the article said.

Consequently, WHO no longer recommends an exclusive vaccine program with the live attenuated virus but rather “recommends that countries that use an attenuated live virus protocol introduce a dose of the inactive polio virus into their routine vaccination program” .