THE world is in the midst of a pandemic caused by the novel coronavirus. Vaccination of the vulnerable in the population has been touted as the key to ending the pandemic.

Drugs, including vaccines, have changed the way in which diseases are treated. Despite all the advantages of drug treatment, evidence continues to mount that adverse reactions and events are recognised risks of drug therapy.

Although used interchangeably at times, there are differences between the terms adverse drug reaction and adverse event.

According to the World Health Organization, an adverse drug reaction is “a response to a drug which is noxious and unintended, and occurs at doses normally used in man for prophylaxis, diagnosis or therapy of disease, or for the modification of physiological function”. An adverse event is defined as an unfavourable outcome that occurs while a patient is taking a drug, but which may or may not be caused by the drug.

Researchers have described an adverse drug reaction as an adverse event with a causal link to the drug. Adverse drug reactions and events are common, frequently preventable causes of illness, disability, and death.

An adverse event following immunisation may be described as any untoward medical occurrence which follows immunisation, and which does not necessarily have a causal relationship with the usage of a vaccine. The adverse event may be any unfavourable or unintended sign, abnormal laboratory finding, symptom or disease.

Pharmacovigilance

Pharmacovigilance supports safe and appropriate use of drugs. Pharmacovigilance has been described by the World Health Organization as “the science and activities relating to the detection, assessment, understanding, and prevention of the adverse effects of drugs or any other possible drug-related problems. It is a fundamental component of effective drug regulation systems, public health programmes and clinical practice”.

Pharmacovigilance of vaccines is of prime importance in the promotion of the safe use of vaccines among their recipients.

Vaccine safety applies to vaccine development and immunisation practices for as long as a product is used. The term vaccine pharmacovigilance defines the science and activities related to the detection, assessment, understanding, and communication of adverse events following immunisation and other vaccine-related or immunisation-related issues, and to the prevention of untoward effects of the vaccine or immunisation, according to the World Health Organization.

In 1789, Wouter van Doeveren, professor of medicine at Leiden University, gave a public lecture entitled ‘Remedio Morbo, Drug Diseases or Ailments Which Often Affect People as a Result of Remedies Administered to Them for Therapeutic Purposes’. Researchers have suggested that Professor van Doeveren’s address could be viewed as the first expression of an emerging scientific interest in adverse drug reactions.

One of the first pieces of evidence of the establishment of a system to monitor drug safety was the committee set up to report on mortalities resulting from anaesthesia in Britain and its colonies. The formation of the committee was in reaction to the 1848 death of a 15-year-old girl who had undergone chloroform anaesthesia for the removal of an ingrown toenail.

However, it was a letter from Dr W G McBride which was published in medical journal The Lancet, suggesting a connection between birth defects in newly born infants and the drug thalidomide, that provided one of the most significant catalysts for drug safety monitoring.

Thalidomide was first manufactured in 1954, introduced to the public in 1956, and was widely prescribed as a harmless treatment for morning sickness and nausea. On November 25, 1961, thalidomide was withdrawn from the market by its manufacturer Chemie Grunentahl. It has been estimated that between 6,000 to 12,000 children have been born with serious birth defects as a result of their mothers’ use of thalidomide.

Underestimated

Adverse drug reactions are ranked as one of the top 10 causes of illness and death in the developed world. While we do not have specific figures for Jamaica, in 2010, researchers at The University of the West Indies, in a study of the types of admissions to the accident and emergency department of the University Hospital of the West Indies, found that 0.6 per cent were related to adverse drug reactions. Additionally, in 2011, research was conducted by Dr J Campbell, which investigated the characteristics of adverse drug reactions from 87 patients, and reported on a retrospective review of 1,600 patients. This body of research revealed a 5.6 per cent prevalence of adverse drug reactions. In other words, 90 of the 1,600 patients had experienced an adverse reaction to a drug. Prevalence is a measurement of all the individuals affected by a disease, or in this case, by an adverse drug reaction at a particular time.

It is noteworthy that the burden of the problem of adverse reactions is underestimated, as in many instances, these reactions are not suspected, leading to underreporting of the problem by health care professionals.

Prior to approval, most drugs will only have been tested for short-term safety and efficacy, on a limited number of carefully selected individuals. These clinical trials exclude elderly individuals, children, drug abusers, and patients with multiple diseases or those who are on multiple medications.

The World Health Organization has stated that in order to identify an adverse drug reaction that occurs in one in 10,000 patients, at least 30,000 patients need to be treated with the drug. Consequently, the limited number of individuals involved in clinical trials do not facilitate good estimation of the adverse drug reaction profile of a drug.

Additionally, the controlled environment of clinical trials bears very little resemblance to the way the drug is used in the wider populations. It is after approval and marketing authorisation by the regulatory bodies when the drug is used on more patients, who have a variety of concurrent diseases and who may be taking other drugs, that previously unidentified adverse reactions (many manifesting years after the release of a drug) may occur. Adverse drug reactions have resulted in withdrawals of drugs from the market.

Vaccines are necessary for overall public health. Up to the time of writing this article, almost 200 million people had already received the approved COVID-19 vaccines. Immunisation with the COVID-19 vaccines will help to improve the body’s immune defence. Adverse reactions reported include fever, chills, headaches, pain at injection site, and generalised ill feeling which are temporary and usually resolve in less than seven days.

Reminders

1. Information about the adverse effects of medications can be found on the labels of over-the-counter drugs or on the printed materials dispensed with prescription drugs.

2. Speak with a pharmacist or physician if you have any questions regarding a drug’s adverse effects.

3. Stop taking a drug if you experience any adverse effects. Contact your physician or pharmacist immediately.

4. Health care professionals and patients should report all adverse drug reactions/events experienced to PharmWatch, Ministry of Health and Wellness.

5. Health care providers have important roles to play in vaccine pharmacovigilance, including gaining and maintaining public confidence in the safety of vaccines.

Dr Jacqueline E Campbell is a family physician, university lecturer and pharmacologist. She is the author of the book A Patient’s Guide to the treatment of Diabetes Mellitus . E-mail her at drjcampbell14@yahoo.com. Dr Cameil Wilson-Clarke is a clinical pharmacist and university lecturer. E-mail her at cameilwilsonclarke@gmail.com.