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By Doris Obinna
Vaccines reduce risks of getting a disease by working with the body’s natural defences to build protection. When one gets a vaccine, the immune system responds accordingly.
The World Health Organisation (WHO) has said vaccines are available “to prevent more than 20 life-threatening diseases, helping people of all ages live longer, healthier lives. Immunization currently prevents two to three million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza and measles.”
Professor of virology, Oyewale Tomori, recently spoke on “Vaccine Production in Nigeria: The Role of Government,” in Lagos. He insisted there are opportunities for vaccines production in the country: “What is needed for its sustainability is adequate funding, national commitment, national pride, accountable transparency and enabling environment.
“The critical success factors for achieving the objective include stakeholder alignment, funding and grants, technology partnership, market access and regulatory certification. By providing this grant, the Federal Government and legislators have demonstrated that there can be responsive governance and a genuine care for the health and welfare of the citizens.”
He recollected that the foundation of the Federal Vaccine Production Laboratory (FVPL) in Nigeria was laid at the Rochfeller Yellow Fever Laboratory, Yaba, Lagos, in 1925; production of smallpox vaccine in sheep in 1930; anti-rabies vaccine production in sheep brain in 1948 and yellow fever vaccine production in 1952.
“Human vaccine production in Nigeria took off from 1940 when Nigeria’s FVPL produced the two vaccines, VF, smallpox and the Anti-Rabies Serum. Facility was shut down in 1991 for upgrade and up until now efforts at revitalising the FVPL have not been successful.”
Director, registration and regulatory affairs, National Agency for Food and Drug Administration and Control (NAFDAC), Dr. Monica Hemben Eimunjeze, said vaccines are biological preparations produced from living organisms that enhance immunity against disease: “The body is exposed to a weakened or dead pathogen, then the body’s immune cells make antibodies to attack the pathogen and, if the body is exposed to the pathogen again, the body will be prepared with antibodies.”
Types of vaccines
Live attenuated vaccines, for example, measles/mumps/rubella (MMR), Eimunjeze said, can be made in several different ways: “Some of the most common methods involve passing the disease-causing virus through a series of cell cultures or animal embryos (typically chick embryos). Using chick embryos as an example, the virus is grown in different embryos in a series.
“With each passage, the virus becomes better at replicating in chick cells, but loses its ability to replicate in human cells. A virus targeted for use in a vaccine may be grown through or ‘passaged through’ upwards of 200 different embryos or cell cultures. Eventually, the attenuated virus will be unable to replicate well (or at all) in human cells, and can be used in a vaccine.
“All of the methods that involve passing a virus through a non-human host produce a version of the virus that can still be recognized by the human immune system, but cannot replicate well in a human host. Protection from a live, attenuated vaccine typically outlasts that provided by a killed or inactivated vaccine.”
Inactivated vaccines, for example, polio, rabies, whooping cough.
Said Eimunjeze: “One alternative to attenuated vaccines is a killed or inactivated vaccine. Vaccines of these types are created by inactivating a pathogen, typically using heat or chemicals such as formaldehyde or formalin.
“This destroys the pathogen’s ability to replicate, but keeps it ‘intact’ so that the immune system can still recognise it. ‘Inactivated’ is generally used rather than ‘killed’ to refer to viral vaccines of this type, as viruses are generally not considered to be alive.”
Conjugate or subunit vaccine, for example, human papillomavirus.
She explained that, “A conjugate vaccine is a type of subunit vaccine, which combines a weak antigen with a strong antigen as a carrier so that the immune system has a stronger response to the weak antigen.
“Both subunit and conjugate vaccines contain only pieces of the pathogens they protect against. Subunit vaccines use only part of a target pathogen to provoke a response from the immune system.
“This may be done by isolating a specific protein from a pathogen and presenting it as an antigen on its own. The acellular pertussis vaccine and influenza vaccine (in shot form) are examples of subunit vaccines.
“DNA and mRNA vaccines are examples of COVID-19 (PfizerBioNTech), while viral vector vaccines are examples of hepatitis B, Ebola and COVID-19 (AZ).
“Viral vector vaccines use a modified version of a virus that is different from the virus being targeted to deliver important instructions to our cells. The modified version of the virus is called a vector virus.
“Also, toxoids are an example of tetanus, diphtheria. A toxoid is an inactivated toxin whose toxicity has been suppressed either by chemical or heat treatment, while other properties, typically immunogenicity, are maintained.”
Vaccine efficacy
Eimunjeze also stated that: “Vaccines are very important to human health. Vaccines promote health, expansive reach, rapid impact and save lives and costs.
“There is a clinical development programme. Also, evidence of clinical efficacy against hospitalizations, severe disease and/or mild symptomatic disease in non-older adults, as well as evidence of induction of neutralising antibody after 1/2 doses in the different groups.”
Locally manufactured vaccines
Tomori maintained that manufacturing vaccines locally enhances better control of supply for immunization: “It helps promotes national security/sustainability and donor fatigue, reduces dependency, and boosts capacity to develop and manufacture vaccines that are relevant to Africa, among other advantages.
“The setbacks detrimental to the production of vaccines in Nigeria include democratic obstacles as well as people making self-interest to override national interest.
“Although the buildings where the productions of vaccines were carried out in the past are now dilapidated, vaccines production in Nigeria is self-interest, turns a 100 meter dash to a marathon.”
