Polio vaccine: see how it works and when to take it

The 2024 National Polio Vaccination Campaign will take place between May 27th and June 14th all over the country. The movement aims to contain the risk of reintroduction of the disease into Brazilian territory.

A polio is an acute contagious disease caused by the poliovirus, which can infect children and adults through direct contact with feces or secretions from infected people. In severe cases, it can lead to infantile paralysis. A polio vaccine and the the only way to prevent the disease and vaccination coverage has been showing results below the target (95%) since 2016, according to the Ministry of Health.

Next, understand how the polio vaccine works and how the current immunization schedule is carried out.

Types of polio vaccine

There are two types of polio vaccine: VOP (Oral Polio Vaccine), which contains the weakened virus and is administered in droplets, and the VIP (Inactivated Polio Vaccine), which contains the inactivated (killed) virus and is administered intramuscularly.

In July last year, the Ministry of Health announced that it will gradually replace VOP with VIP from 2024. The decision was taken after discussion and approval by the CTAI (Technical Immunization Advisory Chamber), which considered recent scientific evidence to protection against disease.

How is the dose schedule currently done and how will it be done after the transition?

Until the transition from VOP to VIP is completed — this is expected to happen in the second half of 2024 — the vaccination schedule is carried out as follows, according to the PNI (National Immunization Program):

• VIP vaccine : three doses in the first year of life (at 2, 4 and 6 months of age);
• OPV vaccine : booster doses at 15 months and 4 years of age, in addition to vaccination campaigns for children aged 1 to 4 years.

After the transition, the VIP vaccine will be used exclusively for immunization against polio . As a result, a polio booster will no longer be administered at age 4. Thus, the scheme offered by the PNI will be three doses (at 2, 4 and 6 months) and only one booster at 15 months of age, with VIP.

Despite the end of the use of OPV, Zé Gotinha, a symbol of childhood immunization, will continue to participate in government campaigns.

Vaccination precautions

According to the recommendations of the SBIm (Brazilian Society of Immunizations), vaccination with any of the vaccines should not be performed on children with moderate to high fever (above 38 ºC). The guideline is to postpone immunization until the clinical condition improves.

Any serious or unexpected symptoms after vaccination must be reported to the service that administered the vaccine. In the case of the OPV vaccine, if there is diarrhea or vomiting, the recommendation is to postpone vaccination or repeat the dose after four weeks . It is also advisable to stop breastfeeding for one hour before and after administering the vaccine.

What are the contraindications?

OPV is contraindicated for pregnant women, people who suffered anaphylaxis after using components of the formula (antibiotics neomycin, polymyxin and streptomycin), people who developed vaccine polio after a previous dose, people with immune system deficiencies, people with HIV and people living with immunosuppressed people.

VIP is only contraindicated to those who have a history of anaphylaxis to the previous dose of the vaccine or any of its components.

Does the polio vaccine cause side effects?

The OPV vaccine, as it contains the live virus, although weakened, can cause adverse side effects, such as:

• Vaccine-associated polio : when the vaccine virus manages to cause polio in the vaccinated person or in those who live with it. This can happen four to 40 days after vaccination. The incidence rate is one case for every 3.2 million doses applied, according to SBIm;
• Aseptic meningitis and encephalitis : it is a side effect considered very rare and with a greater risk for immunodeficient children;
• Allergy reactions : are rare and related to the components of the vaccine;
• Vaccine-derived poliomyelitis : occurs due to genetic instability of the vaccine virus or due to the combination of genetic material from the vaccine virus with other viruses that live in the intestine. By the end of 2013, no VDPV had been identified in Brazil.

In the case of VIP, adverse effects may include mild erythema (inflammatory reaction) at the site where the vaccine was applied, hardening of the region and mild pain. Cases of fever after vaccination are rare.

Where to find the polio vaccine?

Polio vaccines can be found in Basic Health Units and in private immunization services.

Can you get a vaccine with flu or Covid symptoms? Understand