By Michael Gwarisa
Amid growing concerns from parents and guardians over the frequent administration of the Oral Polio Vaccine (OPV), the Ministry of Health and Child Care (MoHCC) has assured the public that the vaccine is safe and necessary to halt transmission.
Zimbabwe’s environmental surveillance detected a vaccine-derived poliovirus type 2 (cVDPV2) strain circulating in sewage systems in Harare’s high-density suburbs, Budiriro, Mbare, and Mufakose, in 2023. In response, the Ministry has been conducting multiple rounds of vaccination campaigns targeting children under the age of 10.
From February 4 to February 7, 2025, Zimbabwe is conducting its fourth round of the novel oral polio vaccine type 2 (nOPV2) campaign for children under 10. However, a snap survey conducted by HealthTimes on Monday, February 3, 2025, revealed that some parents in Harare and Ruwa are hesitant about continued vaccinations due to the repeated nature of the campaign within a short period.
Speaking to this publication, Mr. Norman Dzirambi, the Health Promotion Manager in the Expanded Program on Immunization (EPI), reassured the public that repeated doses pose no harm.
Polio outbreak responses require multiple rounds of immunization to stop transmission. Giving repeated doses to targeted populations does not cause harm but rather strengthens their immune response,” said Mr. Dzirambi.
He further explained that the nOPV2 has undergone clinical trials, and global health authorities have reviewed data confirming its safety and effectiveness in building immunity against polio.
“The nOPV2 is administered orally, two drops in the child’s mouth, similar to other oral polio vaccines. However, it should not be given to pregnant women or immunocompromised individuals, as there is currently insufficient data on how it affects these populations,” he added.
The Ministry of Health has emphasized that the success of vaccination efforts depends on reaching as many children as possible.
“Vaccines are only as effective as the number of children they reach. Stopping the circulation of vaccine-derived poliovirus type 2 (cVDPV2) requires high immunization coverage through well-executed vaccination campaigns,” the Ministry stated.
According to the MoHCC’s Community Mobilisation Training Manual on Polio Vaccination, the nOPV2 was developed to build immunity against the most prevalent strain of cVDPV. It has demonstrated comparable protection to previous polio vaccines and has been approved for emergency use by the World Health Organization (WHO) as a tool for outbreak response.
OPV contains a weakened live poliovirus. When vaccination campaigns fail to reach enough children, unvaccinated individuals remain vulnerable. In rare cases, if the weakened virus is excreted by vaccinated children and circulates in under-immunized communities for extended periods, it can mutate and regain the ability to cause paralysis, much like the wild poliovirus. This risk is higher in areas with poor hygiene and sanitation.
“While this phenomenon is rare, it underscores the importance of maintaining high immunization coverage. If a population is optimally immunized, it is protected from both wild and vaccine-derived polioviruses,” the manual states.
If an outbreak occurs, health authorities must rapidly increase immunity levels through mass OPV immunization. To fully eradicate polio, countries must strengthen disease surveillance and ensure high-quality vaccination campaigns that reach all children.
