A virologist and infectious disease expert, Solomon Chollom, has called for evidence-based post-vaccination surveillance to determine whether people vaccinated against diphtheria have developed adequate immunity, amid fresh outbreaks and deaths across Nigeria.
Chollom in an interview with the News Agency of Nigeria (NAN) said Nigeria’s response to the vaccine-preventable disease should go beyond administering vaccines to assessing their biological and epidemiological impact.
He made the call in Abuja while reacting to the recent diphtheria outbreak in Plateau State, where health authorities have reported 148 suspected cases and 23 deaths.
The Plateau government subsequently ordered the temporary closure of public and private primary and secondary schools from September 7 to contain the spread.
The latest development comes less than a week after the Nigeria Centre for Disease Control and Prevention (NCDC) said Nigeria had recorded more than 10,000 confirmed diphtheria cases in 2026.
According to Chollom, Nigeria has largely operated on the assumption that receiving a vaccine automatically means an individual is protected, without sufficiently examining whether the expected immune response has occurred.
He said post-vaccination surveillance would allow health authorities to collect laboratory evidence on the level of immunity among vaccinated people.
“For too long, we have only assumed that once a vaccine is given, the individual is automatically shielded.
“Unfortunately, this is not the case because of the biology and chemistry that happens between the vaccine and the vaccines. Where this does not click, vaccine failure ensues,” he said.
He identified possible causes of vaccine failure to include problems with vaccine formulation, weaknesses in vaccine logistics, failure to complete the recommended vaccination schedule and inadequate immune response in some individuals.
Chollom said systematic surveillance would help authorities determine whether continued transmission was linked to low vaccination coverage, incomplete vaccination, problems with vaccine delivery or individual immune responses.
He stressed that such evidence was necessary for policymakers to determine the most appropriate response.
The call comes against the backdrop of a worsening outbreak in several states including Plateau, Niger and Kano states.
The ICIR reported on September 2 that the state had recorded 143 suspected diphtheria cases and 23 deaths within two weeks, according to the state Commissioner for Health, Nicholas Baamlong.
Baamlong identified late presentation and difficulty obtaining diphtheria antitoxin as major challenges to the state’s response.
Niger State also has recorded 124 confirmed cases since January and 17 deaths, while Katsina health authorities said about 1,000 suspected cases had been recorded across 29 of the state’s 34 local government areas as of August 28.
Kano has recorded the largest burden among the affected states. Health authorities said on September 1 that 32,633 cases had been confirmed from 39,536 suspected cases recorded since the outbreak began in December 2022, with 1,747 deaths.
The NCDC has identified Kano, Borno and Bauchi among the states carrying the heaviest burden nationally.
Unvaccinated children remain most affected
The NCDC said about 68 per cent of confirmed diphtheria cases were among unvaccinated people.
Its Director-General, Jide Idris, previously attributed continued transmission to inadequate vaccination coverage, vaccine hesitancy, insecurity, displacement and difficulties reaching underserved communities.
These factors have complicated efforts to contain a disease that can largely be prevented through routine childhood immunisation.
In Katsina, for instance, the government began a reactive vaccination campaign on August 25 in 15 high-risk wards across five local government areas, with support from the United Nations Children Fund (UNICEF)
The state said 67,670 people had been vaccinated and announced plans to establish three additional isolation centres.
The Federal Government also activated a multi-agency emergency task force on August 28 to respond to outbreaks in Kano and Katsina.
The task force, comprising the Federal Ministry of Health and Social Welfare, NCDC, National Primary Health Care Development Agency, affected states and international partners, was mandated to strengthen surveillance, close immunisation gaps, improve early case detection and expand access to treatment.
NPHCDA also deployed 500,000 doses of diphtheria vaccine to Kano and Katsina.
Expert seeks testing of circulating strains
Beyond monitoring vaccination outcomes, Chollom urged health authorities to investigate the characteristics of the Corynebacterium diphtheriae strains currently circulating in Nigeria.
He called for rapid antigenic profiling to determine whether the circulating strains had undergone significant changes that could have implications for prevention strategies.
“Another area worth reviewing for learning in this outbreak, is a quick antigenic profiling of the current strains of the organism Corynebacterium diphtheriae, to ascertain if they have changed drastically,” he said.
He said laboratory evidence from such investigations could help authorities understand why transmission continued despite vaccination efforts.
Chollom stressed that the call for post-vaccination surveillance should not be interpreted as a rejection of immunisation.
Rather, he said vaccination remained an important tool for preventing vaccine-preventable diseases, but its effectiveness should be continuously assessed using scientific evidence.
Mustapha Usman is an investigative journalist with the International Centre for Investigative Reporting. You can easily reach him via: musman@icirnigeria.com. He tweets @UsmanMustapha_M