Medicines and vaccines are recalled for a number of reasons, but no COVID-19 vaccines authorized by the World Health Organization for emergency use have been recalled en masse.

Small batches of COVID-19 vaccines have been recalled due to storage or contamination reasons, but this is not due to the formula, ingredients, or makeup of the vaccines. Those batches were never distributed, due to the potential issues that might have occurred if they had been administered.

Some COVID-19 vaccines, including those made by AstraZeneca, Sinopharm, and Johnson & Johnson, were temporarily suspended while evidence was researched to determine whether they should be recalled or withdrawn. The European Medicines Agency (EMA) and the United States Food and Drug Administration (FDA) found that the vaccines' benefits still outweighed the risks, and usage resumed.

The primary role of regulatory agencies like the EMA and the FDA is to ensure the safety of medicines and other products including food, medical devices, blood, veterinary products, cosmetics and more.

The FDA protects and promotes "public health through the control and supervision food and drug products." This means they review medication trial and safety data and then approve and reject drugs and vaccines for manufacturing and sales, based on this evidence. Manufacturers of medicines and vaccines must prove that these drugs are safe for public consumption, must label the drugs accurately, must produce the drugs in sterile and safe environments, and undergo several levels of research, preclinical and clinical trials, and many other phases before applying for authorization from regulatory agencies.

In rare cases, some drugs are recalled after they have become available on the market. A recall is considered the most effective way to protect the public from a potentially dangerous or defective product. These recalls are usually voluntary and occur when a company removes a defective product from the market, either on their own or at the request of the FDA or EMA. Recalls are serious processes that require urgent action in order to protect the health of the public. According to the FDA, about 4,500 drugs and medical devices are recalled on average every year in the United States.

Reasons for recalls vary widely. Recalls can occur for reasons as small as inaccurate labeling or dented packaging, or as large as life-threatening side effects or the need for surgical intervention.

Some of the top five reasons for recalls are:

• Manufacturing defects and deviations such as when oversized or undersized pills or capsules which can lead to drugs being either too weak or too strong.
• Particulate contamination which includes glass, silicone and stainless steel for vials, syringes and IV bags, and even shipping materials that may impact the quality of the medication, vaccine, or device.
• Contamination of active pharmaceutical ingredients which means a drug has some impurities in its liquid or solid form.
• Packaging defects like cracks on the rim of vials that caused the product to no longer be sterile. (In fact, sterility is the leading cause of medical-device recalls).
• Mislabelling or poor packaging with confusing dosing instructions. This can also include a description for a medication on a box that does not match the drug itself.

When medicines pose health or other hazards that may lead to unforeseen side effects, they can be recalled, but this process occurs at different levels. Both the EMA and FDA classify recalls into three categories. Most recalled medicines and products are found in Class II. For the FDA, those classes look like:

• Class I: A dangerous or defective product that could cause serious health problems or death.
• Class II: A product that might cause a temporary health problem, or pose slight threat of a serious nature.
• Class III: A products that is unlikely to cause any adverse health reaction, but that violates FDA labeling or manufacturing laws.

For the EMA, those similar recall classifications look like:

• Class I:  Defects, which are potentially life-threatening or could cause serious risk to health
• Class II: Defects, which could cause illness or mistreatment but are not Class 1.
• Class III: Defects which may not pose a significant hazard to health but where a recall has been initiated (perhaps not required by the competent authority) for other reasons, but are not Class 1 or 2

These agencies then determine how far along the supply chain the recall should go, from transportation to manufacturing to sourcing and beyond.

When the FDA determines a product might need to be recalled, it is usually through adverse event reports. The United States Centers for Disease Control and Prevention routinely monitors the Vaccine Adverse Event Reporting System (VAERS) for any issues that might be occurring in people receiving vaccines. The European Centre for Disease Prevention and Control also monitors vaccine rollouts to look for potential side effects or injuries.

Once a potential issue is identified, the FDA will then conduct a health hazard evaluation with a special committee to review the medicine and consider many topics like the injuries or illnesses caused by the medication, what preexisting conditions might contribute to the illness, how hazardous the medicine is to the populations and especially vulnerable groups, how serious the hazard is and what the level of risk looks like, and what the short- and long-term consequences of the health hazards are.

Despite the fact that many medications must be tested in clinical trials, some safety concerns are not discovered until after medications and vaccines are on the market for a while. Many recalls are minor and may only involve a small batch of a medicine or a very small issue that won't impact a vast majority of patients. However, this tool is extremely valuable to the FDA and EMA in order to protect the safety of the public.

To date, there have only been a few vaccine recalls or withdrawals for any illness. These were based on concerns about how effective the vaccines were or safety challenges they might have posed. Oftentimes vaccine recalls have occur before any injuries have been caused due to the potential safety concerns noted by the manufacturer during quality testing for irregularities.

From January 2013 to October 2018, almost 8,000 medications were recalled by pharmaceutical companies across the world. This is a tiny amount in comparison to the number of medicines that are safely sold and taken every year. However, any recall should be considered a serious event due to the potential injuries that may occur to people who ingest them. Most adverse events are minor, but people should always speak to their healthcare professional if they are experiencing any side effects or injuries following the use of any medications.

The AstraZeneca and Johnson & Johnson COVID-19 vaccines both made headlines recently due to their potential links with adverse events in a small group of people who received the vaccines. After careful review by the EMA and FDA, the benefits of the vaccines were found to outweigh the risks and they were put back into use after these temporary suspensions.