In Summary
  • The disease was a global menace that severely affected large human populations with devastating consequences of death, desperation, blindness and lifetime scars.
  • The cowpox-smallpox beneficial link led to heightened vaccine production and mass human vaccination globally. In 1980, the World Health Organisation (WHO) declared smallpox eradicated globally.
  • The vaccine is given twice per year and protects the animals well. The farm manager, Joshua, who is also a paravet, participated in the exercise.
  • Such adverse vaccine reactions occur in animals in very small proportions of the population. It is estimated to be about one reactor in a million doses of a high quality vaccine.

Edward Jenner, an English scientist, developed and introduced the first successful vaccine in 1796. He made cows to gift humans a lasting solution to smallpox.

The disease was a global menace that severely affected large human populations with devastating consequences of death, desperation, blindness and lifetime scars.

Edward observed that milkmaids infected with cowpox became resistant to smallpox infection. Cowpox in both humans and cattle is a mild viral disease that only causes blisters on the affected parts of the skin and they later heal without leaving any marks.

Jenner went further and demonstrated that when people were inoculated with the cowpox virus, they would not get smallpox when they were challenged with its virus. He termed that process of protection “vaccination” from “vacca”, the latin word for cow. Vaccination may, therefore, be loosely translated as “cownisation”.

The cowpox-smallpox beneficial link led to heightened vaccine production and mass human vaccination globally. In 1980, the World Health Organisation (WHO) declared smallpox eradicated globally.

Since Jenner’s discovery, medical scientists in human and veterinary medicine have developed many vaccines against disease-causing bacteria, viruses and protozoan parasites.

The world again in 2011 declared the deadly rinderpest viral disease that affected mainly cattle eradicated.

These are the only two diseases in the world that have been eradicated by active vaccination, surveillance and education. Many others may eventually follow.

A disease is considered eradicated when it stops circulating in the global population. Elimination, on the other hand, refers to stopping the disease from circulating in specific populations.

One question I keep encountering from farmers is whether vaccines are absolutely safe. Now, unfortunately, the answer is no.

CASE OF ADVERSE REACTION

However, we use vaccines in both humans and animals by taking into account their scientifically determined level of protection against a disease, the frequency of occurrence of adverse reactions and severity of the reactions in the patients.

I had my day with undesirable vaccine reactions last week in Murang’a. My colleague, Dr Veronica, and I had gone to vaccinate sheep, goats and cattle on a farm against foot and mouth disease.

The vaccine is given twice per year and protects the animals well. The farm manager, Joshua, who is also a paravet, participated in the exercise.

We dewormed the animals at the same time. There is no known adverse reaction between the vaccine and the dewormer we were using. We had just completed the vaccination when Joshua drew my attention to a 15-month-old heifer.

The animal was raising and shaking its head. It was producing a lot of saliva and kicking objects. It would also kick the underside of its belly repeatedly and kept attempting to urinate without yielding anything.

The heifer further deteriorated within a short time to staggering and having a high-stepping gait. It was getting into severe breathing difficulties. I quickly decided this was a case of adverse reaction to the vaccine or the dewormer. The heifer had been given both.

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