The first case of wild polio on the African continent in more than five years should serve as a warning to countries with low vaccination coverage against the disease, such as Brazil. The assessment is from the president of the Brazilian Vaccination Society (SBIm), Juarez Cunha, who calls for more campaigns that build trust in vaccinators and remind families to adhere to the childhood vaccination schedule.
“The message that remains is a warning about the risk we face due to low vaccination coverage,” says Cunha. “The numbers reveal this vulnerability. Out of ten children, three are not vaccinated. This is the risk of a completely avoidable situation.
The circulation of wild poliomyelitis in the world has been limited by the success of vaccination against this disease, which is now endemic only in Pakistan and Afghanistan. According to the World Health Organization (WHO), only five cases were reported worldwide in 2021.
On the 17th, however, health authorities in Malawi reported the first wild case of poliomyelitis in Africa in more than five years and declared an outbreak of poliovirus type 1. For WHO Regional Director for Africa, Matshidiso Moeti , “As long as poliomyelitis exists anywhere in the world, all countries remain at risk of importing the virus.
Poliomyelitis was declared eradicated from Brazil in 1994, also thanks to the success of the vaccination campaign. Despite this, since 2015, the country has failed to meet the target of 95% of the target audience vaccinated, a level necessary for the population to be considered protected.
Administered in drops, orally, the attenuated vaccine is applied at 15 months and 4 years – Archives / Brazil Agency
In Brazil, two different vaccines are used to immunize against poliomyelitis, also known as infantile paralysis: the inactivated and the attenuated. The inactivated vaccine should be given to babies aged 2, 4 and 6 months. The attenuated vaccine, administered in drops orally, is indicated at 15 months and 4 years.
According to the National Vaccination Program Information System (SI-PNI), polio vaccination coverage was 67.66% in 2021, but only 52.49% of children reached the planned dose for the age of Four years. In the Northeast and North regions, the situation is even worse, with percentages of 42% and 44% for complete immunization, respectively.
Juarez Cunha recalls that low vaccination coverage has already been responsible for the return of the circulation of measles, which was declared eradicated in the Americas in 2016 and returned to infect people in Brazil in 2018. Poliomyelitis remains asymptomatic, making the symptomatic cases detected are even more worrying.
“80% of people infected with poliomyelitis have no symptoms. So, if a case has been identified that led to poliomyelitis, that means Malawi is probably circulating the virus. Where there is a case, it is already very worrying,” said the president of the SBIm.
The case recorded in Malawi was linked to the strain of the virus circulating in Sindh province, Pakistan, and, according to the WHO, does not change the certification of Africa as a wild polio-free region, granted in 2020. Due to its low vaccination coverage, however, the African continent still coexists with cases of vaccine-derived poliovirus, since the attenuated vaccine contains the live and weakened virus.
In rare cases, the attenuated virus is able to replicate in the human gut, mutate and spread, even with reduced capacity, through faeces, if the surrounding population is not immune, a risk that increases if it circulates in a region with sanitation and housing. problems. The longer the virus can circulate, the greater the chance of further mutating and regaining the ability to cause paralysis.
Juarez Cunha explained that in Brazil, the risk of contracting vaccine-derived poliovirus is lower because children only receive the attenuated vaccine as a booster after they have already been immunized with three doses of the more effective inactivated vaccine. and safer. because it contains the “dead” virus. Even so, he warns that the risk exists and should be minimized with high vaccination coverage.
“The least favored populations are those with the lowest vaccination coverage. It is a vulnerability that is added to another vulnerability, because it is precisely where we have the least possibility of control, hygiene and access to the sewage network, ”said the doctor.
The president of the SBIm declared that with such risks, it is necessary to invest in communication to inform about the vaccination schedules and to reinforce the confidence of the population in the vaccines. “Unfortunately, we have no communication from the Ministry of Health regarding routine vaccines. We need to strengthen the PNI and the communication from the Ministry of Health,” he says. “Although people do not know about poliomyelitis, because they have been vaccinated, the disease still exists and is likely to come back. This message must be conveyed and the message of confidence in vaccination, which has not been conveyed by governments, institutions and even health professionals. health, especially for the covid-19 vaccine, but this ends up impacting all vaccines.
Brazil without cases since 1990
search by Brazil Agencythe Ministry of Health responded that Brazil had not detected cases of the disease since 1990 and in 1994 received certification from the Pan American Health Organization (PAHO) as an area free of wild poliovirus circulation on its territory, with the other countries of the Americas.
“The ministry carries out communication actions throughout the year, not only during vaccination campaigns, to reinforce information on the safety and effectiveness of vaccines as a public health measure,” the ministry said. , who also pointed out that polio vaccination coverage was 76.05% in 2020 and 67.66% in 2021.
“As for the first booster, the vaccination coverage is 68.32% in 2020 and 58.07% in 2021. All these data are still preliminary and therefore subject to change,” added the Ministry of Health.