Low polio vaccine coverage raises alert for risk of disease return

Brazil is at risk of a return of poliomyelitis, a disease caused by the polio virus that had been eradicated in the 1990s, when the country became a place free of the pathogen.

However, the fall in vaccination coverage and the decrease in the feeling of danger of the disease, combined with a series of structural difficulties of the PNI (National Immunization Program), put in check the certificate of polio eradication. And, in the last two years, the Covid pandemic has further aggravated this scenario.

In September, PAHO (Pan American Health Organization), the WHO (World Health Organization) arm in the Americas, declared Brazil a very high risk country for polio.

According to the pediatrician and vice president of the Brazilian Society of Immunizations (Sbim), Isabella Ballalai, the country’s very high risk alert is due to a vaccination coverage below 95% in children under five years old with the possibility of reintroduction. of the virus at any time, as recently happened in New York, the first case in the Americas since 1994.

“This risk is defined by several criteria, and Brazil, in addition to not reaching the recommended vaccination coverage, also fails to comply with the other criteria”, says the doctor.

Currently, in the country, the vaccination coverage of poliomyelitis in children up to five years of age is at 61%, according to data from the SI-PNI obtained by the DataSUS platform. In previous years, this rate had already fallen, from around 80% in 2016 to 70% in 2020.

The still incomplete data for this year show that the lowest vaccination coverage rate in the country is concentrated in the North (38.8%) and Northeast (41%) regions, while the highest coverage is in the Midwest (46.6% ).

The vaccination schedule for children under five years old consists of a primary schedule, with an inactivated virus vaccine (called VIP) of three doses, at two, four and six months. The booster is already done at 15 months and at four years of age, with the oral vaccine of attenuated virus, the famous “droplet” vaccine.

The report heard six experts to understand the current situation in Brazil and, according to them, first of all, it is necessary to understand that the decrease in vaccination coverage is a phenomenon that has multiple factors and is not exclusive to the country.

“The drop in vaccination coverage is a global phenomenon, not just here, and it has been happening since 2016 and 2017. In 2018, after a great national mobilization with health managers, we managed to recover [a cobertura vacinal]but this drop was accentuated in 2019 and, with the pandemic, this work was hampered”, explains the epidemiologist and former coordinator of the PNI (from 2011 to 2019), Carla Domingues.

According to Domingues, some of these factors are the perception of lack of risk of the disease, once it has been eradicated, the lack of knowledge of the importance of vaccination and, more recently, the dissemination of misinformation about immunization.

“If the population does not see that disease as something serious, although they think it is important to vaccinate, they will not prioritize vaccination, and this is one of the factors that contributed to the fall”, he says.

In addition, the difficulty in accessing the vaccine, given the size of the Brazilian territory and regional differences, is another factor.

“A city the size of São Paulo has its strategies to expand vaccination, such as opening clinics on weekends, at night. But these strategies are not the same as in Amazonas, where it is necessary to think of a strategy to lead to vaccine actively for the population”, he says.

These activities, however, have been hampered in recent years with the decrease in resources aimed at communication, training and prioritization of the national vaccination campaign, according to infectologist Julio Croda, a researcher at Fiocruz.

“The lower coverage in the North and Northeast of the country brings reflection with regard to access and what is being actively done. The lower the presence of family health policies in the municipality, the more difficult it will be to increase coverage”, he explains.

For the infectologist, it would be important, in the current scenario, unified strategies for prioritizing vaccination. “If that father or mother is unable to take the child to be vaccinated at the post during working hours, trying to campaign in schools, doing an active search, these are strategies that can work and improve coverage.”

The same vision is shared by pediatrician and associate professor at the Faculty of Medicine of USP Gabriel Oselka. “No one knows about a case of poliomyelitis anymore, there is no such perception of risk. Before, the entire adult population was ‘immunized’ by the so-called herd immunity because of high vaccine coverage and today, with the lack of risk perception, this has already ceased to be a reality.”

The doctor, who coordinated immunization actions in the state of São Paulo, also recalls that this vision, combined with fake news, created fertile ground for the activities of anti-vaccination groups in recent years.

The drop in coverage, combined with two other factors for which there is little information in the country, such as environmental surveillance (search for samples of the virus in sewage networks) and the notification of so-called adverse effects related to the vaccine, may still mask the real dimension of the circulation of polio in the country, explains the director of immunizations of the SBP (Brazilian Society of Pediatrics), Renato Kfouri. “The introduction of the oral vaccine as a booster at 15 months [1 ano e meio] and 4 years causes the virus to be naturally shed in feces, but we do little surveillance of the virus in sewage networks.”

For the epidemiologist and professor at the Federal University of Espírito Santo (Ufes) Ethel Maciel, it is necessary to completely replace the attenuated vaccine with the inactivated virus. “In a country like Brazil with many families without basic sanitation and a scenario of low vaccination coverage, it is undoubtedly worrying to throw the vaccine virus into the sewer, which could cause a reintroduction of the virus.”

One of the cases of notification of a serious adverse effect possibly related to the vaccine occurred on the 6th, in Pará, when the State Health Department notified the presence of poliovirus in the feces of a child with acute flaccid paralysis, which may be a related effect. to the vaccine. The Ministry of Health has not yet completed the investigation.

In Maciel’s assessment, the recovery of vaccination coverage must necessarily go through a public policy of prioritizing immunization. “Undoubtedly, the questioning by health authorities of the safety and efficacy of vaccines contributed to this decrease in coverage. The operationalization of campaigns, which is by the municipalities, has still worked, but if there is no intention in the three spheres to encourage vaccination, it will be difficult to recover.”