Low polio vaccination raises alert in Brazil

Poliomyelitis cases in countries that have not been registered for years have recently raised the alarm for the disease that causes infantile paralysis. In Brazil, the disease caused by poliovirus continues to be characterized as eliminated, with no occurrences since 1990, but PAHO (Pan American Health Organization) has already stated that the country is at high risk for the disease to return.

“Brazil was almost classified as very high risk [para o retorno da pólio]. Of all the other countries classified as high risk, it is the closest to the highest risk category”, says Luíza Arlant, president of the Technical Chamber for the Certification of Poliomyelitis Eradication in Brazil with PAHO/WHO (World Organization for Health).

According to her, there are several factors in the assessment made by the organization, such as health surveillance, conditions for coping with a possible new case and, mainly, vaccination coverage – according to the Ministry of Health, vaccination against polio has had results below the target since 2016. .

In 2021, the worst recent year, only 67% were achieved in polio vaccination coverage.

The folder states that “it closely monitors vaccine coverage and has worked to intensify the strategies necessary to reverse the scenario of low coverage”. The ministry also says that, in the last three years, it has carried out multi-vaccination campaigns to update the population’s portfolio.

According to PAHO information, polio causes symptoms in approximately 5% to 10% of infected people. In some cases, it results in paralysis of the arms and legs and can also affect the respiratory system, leading to death.

The most recent diagnoses of concern to the medical community were in Malawi and Israel. In the first country, a case of wild virus was registered, the one that circulates normally in nature. The problem is that until then, polio was considered endemic by this type of pathogen in only two nations: Afghanistan and Pakistan.

In Israel, a child was infected by the vaccine virus, a strain that comes from the Sabin vaccine — the “droplet” vaccine against polio.

“The oral polio vaccine [Sabin] is composed of an attenuated virus and therefore can transmit the virus from person to person: the individual takes the vaccine, it goes to the digestive system and this vaccine virus is eliminated through the feces to the environment”, explains Isabella Ballalai, pediatrician and vice-president of Sbim (Brazilian Society of Immunizations).

However, cases of vaccine virus infection do not indicate that the vaccine is the cause of the disease — in fact, it was essential to eliminate polio in recent decades in several countries, including Brazil, highlights Juarez Cunha, pediatrician and president of Sbim .

“Because of the way we had the Sabin vaccine, which is very easy to produce, apply and with very good effectiveness, it was widely used in all countries of the world”, completes the pediatrician.

In addition, data from Sbim indicate that there are very low cases of vaccine-associated poliomyelitis — on average, only one case for every 3.2 million doses applied.

The problem with polio is when vaccination coverage is low, causing the virus — regardless of whether it is vaccinated or wild — to spread through the population. This was precisely the case in Israel, as the child in question had not been vaccinated.

In addition to the vaccination coverage that needs to be comprehensive, another necessary initiative is the priority of application of the inactivated vaccine – known as Salk. It, unlike Sabin, is injectable and does not cause the so-called vaccine virus.

“If our coverage is too low, there is a risk of what happened in Israel: a vaccine virus carrying the disease. This does not happen if the child is previously vaccinated with the inactivated immunizer. In Brazil, for example, any child who is overdue will always receive the inactivated one, to protect against the potential risk of a vaccine-derived virus”, explains Cunha.

Therefore, since 2016, the WHO recommends that at least one of the doses of the vaccine schedule be with the inactivated model.

In Brazil, three doses of the Salk type are recommended and the other two reinforcement applications of the “droplet”, Sabin. This scheme was adopted in 2016 in the PNI (National Immunization Plan). Before that, the country had incorporated two doses of Salk, in 2012.

For the future, the expectation is that the Sabin vaccine will no longer be used, in order to have the total eradication of the disease.

“The WHO’s idea is to migrate completely to the inactivated vaccine, but this is still not possible, because it does not have the production capacity to make vaccines that are only inactivated worldwide”, says Cunha.

Arlant also explains that it is important, in situations of greater danger for polio outbreaks, to opt for the oral vaccine because it has “the great benefit of stimulating the intestinal mucosa, which increases the level of protection”.

One of those cases in which there is a danger of the disease returning is what is happening now: low vaccination coverage in Brazil amid a resurgence of cases in some parts of the world.

“In a time of outbreak, it is recommended to use an oral vaccine with attenuated virus, but in normal times, countries have to opt for the inactivated vaccine”, summarizes Arlant.

Another point to be considered is health surveillance, as in cases of acute flaccid paralysis, since poliomyelitis causes this condition. “If I have a person with this paralysis, I can’t help but investigate and report whether it was caused by polio or not,” Ballalai says.

This point is also out of date in Brazil. According to a technical note from the Ministry of Health published in October 2021, there is “non-compliance with the targets of the epidemiological surveillance quality indicators [de paralisia flácida aguda] in children under 15 years of age”.

In a new note, the ministry explained that “between 2012 and 2021, Brazil achieved three of the four indicators”. The one that is below the expected is the timely collection of feces, which needs to be done within 14 days.

In addition, Ballallai says it is important to improve communication to raise awareness among the population. In years ago, with the rise of vaccination, scenes of people with polio sequelae became increasingly rare — and the population’s sense of risk diminished. That’s why a warning message of the danger that polio could be coming back is needed, she says.

understand polio

What are the main symptoms and sequelae of polio? The most recognized sequel is limb paralysis, but the disease can also cause joint pain, osteoporosis, muscle atrophy, difficulty speaking, among others. Symptoms include body aches, fever, diarrhea, vomiting, neck stiffness and spasms.

Who can be vaccinated against polio through SUS? The Ministry of Health recommends vaccination in children aged between two months and four years. There are, however, cases in which vaccination is recommended for people over five years of age, such as when there is a trip to a country that is experiencing an outbreak of the disease and the vaccination schedule is not yet complete.

How many doses make up the polio vaccination schedule? In total, there are five applications. The first dose should be at two months of age. The second should be applied at four months and the third at six. In addition, there are two boosters: the first at 15 months and the second at four years of age. The first three doses are made with the injectable vaccine (Salk) and the last two with the droplet version (Sabin).

In addition to vaccination, are there other ways to prevent the disease? To avoid poliovirus infection, it is also important to take care of basic hygiene and have an efficient basic sanitation system.

When will the 2022 polio vaccination campaign be? According to the Ministry of Health, this campaign should take place in the second half of the year. At the same time, there will also be multi-vaccination campaigns to update the vaccination record for children and adolescents, according to information from the folder.