When a patient gets a biosimilar instead of the original biologic drug, they’re not getting a copy like a generic pill. Biosimilars are made from living cells - think of them as close cousins, not twins. That’s why tracking side effects isn’t as simple as checking a pill bottle. In 2026, adverse event monitoring for biosimilars is more complex than ever, and getting it wrong can mean missed signals, delayed responses, or worse - patients harmed because no one knew which drug caused the reaction.
Why Biosimilars Need Special Safety Tracking
Unlike small-molecule generics, which are chemically identical to their brand-name counterparts, biosimilars are made in living systems. Even tiny changes in temperature, pH, or manufacturing steps can alter their structure. These differences don’t make them unsafe - but they can affect how the immune system reacts. That’s why immunogenicity, or the risk of triggering an unwanted immune response, is the biggest concern.For example, if a patient develops antibodies against a biosimilar used to treat rheumatoid arthritis, it could make the drug stop working - or worse, cause a serious allergic reaction. The same thing could happen with the reference product. But if you can’t tell which one the patient got, how do you know if the problem is with the biosimilar or the original?
That’s the core challenge of biosimilar safety monitoring: distinguishing signals. The system has to catch rare side effects - maybe one in 10,000 patients - while sorting through millions of reports from doctors, pharmacies, and patients. And it has to do it without confusing one biosimilar with another, or with the reference product.
How Adverse Events Are Reported Today
Most countries rely on two main systems: spontaneous reporting and active surveillance.Spontaneous reporting means healthcare providers or patients report side effects after they happen. In the U.S., that’s the FDA’s FAERS system. In Europe, it’s EudraVigilance. In Canada, it’s Health Canada’s Canada Vigilance Program. These systems collect reports from hospitals, clinics, and drug manufacturers. Serious events must be reported within 15 days. Non-serious ones within 90 days.
But here’s the problem: most reports still use brand names. A 2022 Health Canada report showed 87.3% of biologic adverse event reports used the brand name, not the generic or biosimilar name. That’s fine if the doctor writes down exactly what was given. But too often, they don’t. A 2022 survey of U.S. physicians found 63.4% were confused about how to document biosimilars. Oncologists and hematologists - who use these drugs most - had the highest confusion rates, at 81.7%.
Active surveillance is the next level. Systems like the FDA’s Sentinel Initiative dig into electronic health records, insurance claims, and pharmacy databases to find patterns. They don’t wait for someone to report a problem - they look for it. This is where real-world data becomes powerful. If a spike in kidney inflammation shows up in patients taking a specific biosimilar, but not others, that’s a signal.
The Naming Problem: Suffixes, Brands, and Confusion
In 2017, the FDA started requiring biosimilars to have a four-letter suffix - like “-abp21” for Amjevita. The idea was to make tracking easier. But in practice, it hasn’t worked as planned.Doctors don’t always write the suffix. Pharmacists don’t always label it. Patients don’t know what it means. A 2023 Medscape post from a Johns Hopkins rheumatologist said she now writes down both the brand name and manufacturer because “the pharmacy substituted the biosimilar without documentation - making adverse event attribution impossible.”
Canada doesn’t use suffixes. Instead, they require the brand name to be reported. That’s why 87.3% of reports use brand names - because that’s what’s required. Spain, meanwhile, started mandating biosimilar identification in electronic health records in 2020. Their reporting accuracy jumped from 58% to 92%.
Patients are caught in the middle. The Arthritis Foundation’s 2022 survey found 41.2% of people on biosimilars didn’t know which specific product they were getting. That’s not just inconvenient - it’s dangerous. If someone has a bad reaction and can’t tell if it was the biosimilar or the reference drug, the whole system breaks down.
Regulatory Differences Around the World
The U.S., Europe, and Canada all have different rules - and that matters.The European Medicines Agency (EMA) treats biosimilars the same as reference biologics. No extra requirements. Their 2021 guide says: “No specific safety requirement applies only to biosimilars.” That’s because their system relies on strong traceability and real-world data. They’ve approved 43 biosimilars as of 2022, and their reporting system is mature.
Canada is stricter. Their 2022 Handbook says biosimilar Risk Management Plans must include “detailed information on how the immunogenicity potential will be monitored” and “methods to distinguish adverse event reports for the biosimilar from those for other licensed products.” They also started enforcing mandatory manufacturer identification in reports on January 1, 2023. Non-compliance can cost up to $500,000 CAD.
The U.S. is a hybrid. The FDA requires biosimilar makers to submit safety reports every six months for the first two years after approval, then annually. They also use the 21st Century Cures Act to scan FAERS every two weeks and publish quarterly reports. But the lack of consistent naming and poor EHR integration means many reports are useless.
What’s Working - and What’s Not
There’s good news: real-world data confirms biosimilars are safe. A 2016 Danish study found no difference in adverse event profiles between biosimilars and reference products. The EMA’s 2023 performance report showed their AI tool, VigiLyze, detects safety signals with 92.4% accuracy.But the system is still fragile. In 2021, IQVIA found biosimilar-specific reports made up only 0.3% of all biologic reports - even though biosimilars accounted for 8.7% of prescriptions. That’s underreporting. It’s not that biosimilars are unsafe. It’s that we’re not seeing the full picture.
Why? Three big reasons:
- Doctors don’t know how to document biosimilars correctly.
- Hospitals don’t have systems that capture the manufacturer or lot number.
- Patients don’t know what they’re taking - and aren’t asked.
A 2021 study found only 37.8% of U.S. pharmacists knew the right way to report biosimilar adverse events. Only 42.6% of U.S. hospitals had fully implemented EHR systems that could capture the exact biosimilar name.
The Future: AI, Traceability, and Global Standards
The next wave of improvement is coming from technology and policy.AI tools are being trained to scan unstructured clinical notes - doctor’s handwriting, discharge summaries, nurse’s notes - to pull out biosimilar names and side effects. Companies like ArisGlobal and Oracle Health Sciences are building cloud-based platforms that cut implementation time by 40%. But it’s expensive: $250,000 to $500,000 for mid-sized firms.
Traceability is the biggest priority. The International Pharmaceutical Regulators Programme is pushing for a global Unique Device Identifier (UDI) system for biologics by 2026. Think of it like a barcode on every vial - with lot number, manufacturer, and batch info. Pilot studies in Switzerland showed this could reduce attribution errors by 73.5%.
WHO’s 2023 report warns that current systems won’t handle the expected 300+ biosimilars by 2030. Right now, 87.2% of regulators lack standardized protocols to assess immunogenicity. That’s a ticking clock.
What Patients and Providers Can Do Today
You don’t need AI or new laws to help. Here’s what works right now:- If you’re a patient: Ask your pharmacist or doctor what biosimilar you’re getting. Write it down. Keep the label. If you feel worse after a switch, report it - and say which product you took.
- If you’re a provider: Always document the full name - brand, manufacturer, and lot number if possible. Don’t assume the pharmacy told you correctly. Use the suffix if it’s there.
- If you’re a pharmacist: When substituting, confirm the prescriber’s intent. Document the change. Don’t let convenience override safety.
There’s no magic fix. But the system won’t improve unless everyone - patients, doctors, pharmacists, regulators - starts treating biosimilar safety like a shared responsibility. Not a regulatory checkbox. Not a cost-saving trick. A matter of trust.
Why This Matters for People With Chronic Illness
Biosimilars aren’t just cheaper versions. They’re lifelines. For people with rheumatoid arthritis, Crohn’s disease, or cancer, they mean access to treatment that was once too expensive. But that access only works if the drugs are safe - and if we can trust the data when something goes wrong.Imagine a patient on a biosimilar for multiple sclerosis. They develop a rare brain infection. If we can’t tell if it’s the biosimilar or the reference drug, we can’t fix the problem. We might pull a safe drug off the market. Or we might keep giving a dangerous one.
That’s why adverse event monitoring for biosimilars isn’t just about compliance. It’s about keeping patients alive.
Are biosimilars safer than generics?
No - but they’re not the same. Generics are chemically identical to brand-name pills. Biosimilars are highly similar to complex biologic drugs made from living cells. Because they’re not exact copies, they need more careful safety tracking - especially for immune reactions. Both are safe when properly monitored, but biosimilars require more detailed reporting and traceability.
Why do biosimilars have suffixes like -abp21?
The FDA added four-letter suffixes in 2017 to help track which biosimilar caused a side effect. But in practice, doctors and pharmacists often don’t use them. The suffix is meant to distinguish between similar drugs, but if it’s not written down or recorded in medical records, it doesn’t help. Some countries, like Canada, avoid suffixes and instead require brand name reporting.
Can biosimilars cause different side effects than the original drug?
Regulators require proof that biosimilars have no clinically meaningful differences in safety or effectiveness. Real-world data from Denmark, the EU, and the U.S. show side effect profiles are nearly identical. But because biosimilars are made from living cells, tiny differences can affect immune responses. That’s why immunogenicity is closely watched - not because they’re unsafe, but because we need to detect any rare differences early.
What happens if a patient has a bad reaction but doesn’t know which drug they got?
The report becomes useless for tracking. If a hospital or pharmacy doesn’t record the exact manufacturer or lot number, regulators can’t tell if the issue is with one biosimilar or another - or the original drug. This is why patient education and provider documentation are critical. Without accurate reporting, safety systems can’t work.
How can I report an adverse event from a biosimilar?
In the U.S., report to the FDA’s MedWatch program. In Canada, use Health Canada’s Canada Vigilance portal. In Europe, contact your national medicines agency. Always include: the drug name (brand and manufacturer), lot number if available, your symptoms, and when they started. Even if you’re unsure which product you received, report it - and say so. Every report helps build the data.
Is it true that biosimilars are underreported?
Yes. In 2021, IQVIA found biosimilar-specific reports made up just 0.3% of all biologic reports - even though biosimilars were used in 8.7% of prescriptions. That gap suggests many side effects aren’t being linked to the right product. The main reasons: poor documentation, lack of training, and confusion over naming.
What’s being done to improve biosimilar safety tracking?
Several things: AI tools are being trained to scan clinical notes for biosimilar names. Canada now requires manufacturers to be clearly identified in reports. The EU uses AI-powered signal detection. The WHO and ICH are working on global standards. And by 2026, a global unique identifier system for biologics may be rolled out - like a barcode on every vial - to track exactly which batch a patient received.
What Comes Next
The number of biosimilars will keep growing. By 2028, the market will be worth over $34 billion. That means more drugs, more patients, more data - and more pressure on the system.The goal isn’t to make biosimilars perfect. It’s to make the safety system smart enough to catch problems before they spread. That means better labeling, better training, better technology - and better communication between everyone involved.
Patients deserve safe, affordable treatments. But they also deserve to know what they’re taking - and to trust that if something goes wrong, someone will notice.
Beth Templeton
So we spent billions on biosimilars just to make tracking them harder? Brilliant.