This article was originally posted in the Montreal Gazette.
With COVID-19 cases on the rise again, many people were shocked to discover that rapid tests are no longer available at pharmacies. Having blissfully ignored the problem for the past several months, many were left wondering how to get tested and whether their old tests were still effective or were now expired.
Before delving into the issue of expiry dates, rapid tests are still available, just not at pharmacies. They can be found at the government’s points of service — the vaccination centres, though some people (children under 17, full-time students, etc.) can still get rapid tests at pharmacies. So if any doubt remains about the validity of your rapid COVID tests, the simple solution is to get a new one.
But many of the rapid tests people have in their homes are probably still valid despite the published dates on the box. Both Health Canada and the Food and Drug Administration in the United States extended the expiry dates to two years after the manufacturing date.
To understand why this happened, we first have to explain what an expiration date is and why this is different from the “best before” date you see on food. Anything with a shelf life over 90 days has no requirement for a date labelling. Less than 90 days requires a “best before” date to denote how long it maintains its freshness, taste or nutritional value — not necessarily when it becomes unfit for consumption. Only certain foods require true “expiration dates.”
Medications also have expiration dates. Every year the Drug Enforcement Agency in the U.S. has a Take Back Day where they collect unused, expired medication from people across the country. In 2023, they collected 332 tons of expired meds.
The worry with expired medication is that they will degrade over time and lose their effectiveness. To judge how long this process will take, companies usually perform accelerated stability testing on their new products. They subject them to extreme temperatures and conditions, then extrapolate how long they would last under standard conditions. Many medications may still be fine to use beyond these dates; they just haven’t been tested to prove the point.
The FDA can extend the expiry dates of products by performing updated stability testing, but there’s rarely a compelling need to do so for most products. An important caveat is that extending the expiry date implies unopened bottles and packaging, as being exposed to ambient air and humidity can accelerate the degradation process.
With the case of COVID rapid tests, the decision to extend the expiry dates is easily understandable. Since many people have unused stockpiles of rapid tests in their homes, not updating the expiry dates would have led to unnecessary waste.
With medication, product degradation can lead to a lack of efficacy or potential harm. An EpiPen that has expired may not save your life if you are having an allergic reaction. With COVID tests, the concern is not so much one of safety. The worry is that the test will produce inaccurate results, mainly false negatives.
A positive result depends on the COVID antigen on your nasal swab interacting with labelled antibodies in the test kit to produce a colour change. If the antibodies in the test kit degrade over time, they won’t generate that reaction to signal a positive test, even if you are sick.
So to the question of whether you can use an expired COVID test, the answer is first to make sure that it actually is expired, because it might not be.
Again, the worry is that an expired test might produce a false negative. False positives are unlikely. So if any doubt remains, the first option is the simplest: Go get a new package at a government vaccination centre when you go for your flu / COVID boosters this fall. That will remove all doubt.
