Rebif® (interferon beta-1a) is in the class of drugs called interferons. There are other treatments available that may sound similar, such as Avonex® (interferon beta-1a) and Plegridy (peginterferon beta-1a), but they are not the same product. They may differ in many ways including formulation, method of delivery, frequency, and dose.

Head to head is the only way to compare

The only way to know if one drug is more effective than another is if they were evaluated in the same study. Comparing one study against another is tricky because different studies may have different criteria such as: goals of study, ways data were evaluated, length of the study, and patient populations.

Rebif was proven superior to Avonex

We put Rebif in a head-to-head study against Avonex called EVIDENCE.* For an average of 64 weeks, Rebif 44 mcg was given to 339 people 3 times per week under the skin, with injections at least 48 hours apart. Avonex 30 mcg was given to 338 people once per week into the muscle.

The results were significant. High-dose, high-frequency Rebif was proven superior to low-dose, low-frequency Avonex in 2 important ways:

  1. More people on Rebif remained relapse free than people on Avonex at 64 weeks

  1. More people on Rebif showed no new or enlarging lesions at 64 weeks

With Rebif (44 mcg, 3 times a week under the skin): 58%—nearly 6 out of 10 people—showed no new or enlarging T2 active lesions on an MRI.

With Avonex (30 mcg, 1 time a week into the muscle): 38%—less than 4 out of 10 people—had the same results.

With Rebif (44 mcg, 3 times a week under the skin): 58%—nearly 6 out of 10 people—showed no new or enlarging T2 active lesions on an MRI.

With Avonex (30 mcg, 1 time a week into the muscle): 38%—less than 4 out of 10 people—had the same results.

The exact correlation between MRI findings and the current or future clinical status of patients, including disability progression, is unknown.

Rebif was proven to work better than another in a class I clinical trial. In fact, the FDA approved Rebif based on these results compared with Avonex, among other considerations. If you’re currently on Avonex and not doing as well as you expected, talk to your doctor about switching to Rebif.

* EVidence for Interferon Dose-response: European North American Comparative Efficacy. The EVIDENCE trial was conducted entirely in North America and Western Europe.
New or enlarging lesions detected with PD/T2-weighted MRI.
According to the American Academy of Neurology, data from class I studies are collected under the highest scientific standards and are thought to be the most valid.

Important Safety Information

In the EVIDENCE study, side effects were generally similar between Rebif and Avonex. Differences included:

  • People taking Avonex had more flu-like symptoms than those taking Rebif.
  • People taking Rebif had a greater number of injection-site disorders, liver problems, and decreased white blood cell counts.

Did you know that people who transitioned from Avonex to Rebif achieved further reduction in flare-ups?

When people who participated in the first part of the EVIDENCE study were done, they were asked whether they wanted to continue in the study taking Rebif or leave the study.

Those who chose to stay in the "extension phase" and transitioned from Avonex to Rebif had 50% fewer flare-ups§ after an average of 8 months of Rebif treatment, compared with their last 6 months on Avonex. People in the extension phase who had been on Rebif 44 mcg the whole time had 26% fewer flare-ups.

Here’s how the study worked

605 people remained at the end of the head-to-head phase of the EVIDENCE study. A total of 495 people participated in the extension phase of the EVIDENCE study, which lasted an average of 8 months. In the extension phase, all patients were offered the option of either taking Rebif 44 mcg or leaving the study. 73% of those taking Avonex 30 mcg chose to take Rebif 44 mcg, while 91% of those taking Rebif 44 mcg 3 times a week chose to stay on Rebif 44 mcg.

Important Safety Information

Compared with Avonex, side effects were generally similar. People taking Avonex had more flu-like symptoms than those taking Rebif. People taking Rebif had a greater number of injection-site reactions, elevated liver enzymes, and decreased white blood cell counts; these events also occurred more frequently with Rebif posttransition versus prior use of Avonex.

§ Annualized flare-up rate: Rebif 0.32 vs Avonex 0.64.

Edress's story: Making a choice

I was angry with MS because my son was worried about me—a role reversal I never wanted to happen. So I decided right then and there that I was not going to let MS overshadow my family. I decided to take responsibility for my health and accepted that MS was going to be part of my life.

That meant I had work to do and decisions to make. So that very day, I began educating myself about MS. I read articles from the Internet, books from the library, and pamphlets from my doctor's office. I also met other people with MS who shared lots of helpful information. Most importantly, my doctor and I discussed treatment options. The first therapy my doctor prescribed was Avonex. But after two years, I'd had four relapses. When I was in the ER after a relapse, the neurologist that was treating me in the hospital talked to me about Rebif, and told me that in a high-quality, head-to-head study, Rebif had shown better efficacy in reducing relapses. So I talked to my doctor, and together we made the decision to start Rebif.

While it didn't happen overnight, my doctor and I believe that I've experienced fewer relapses. And that's given me the confidence that I'm doing what I can to help treat my relapsing MS. I'm glad that I made the choice to begin treatment with Rebif.

Edress W.Dog enthusiast, MS LifeLines Ambassador, living with relapsing MS

This story reflects the personal experience of one person. Results and experiences vary from patient to patient.

Next: Rebif was proven effective
Important Safety Information and Indication

Important Safety Information


Before beginning treatment, you should discuss the potential benefits and risks associated with Rebif with your healthcare provider.

Rebif can cause serious side effects. Tell your healthcare provider right away if you have any of the symptoms listed below while taking Rebif.

  • Behavioral health problems, including depression and suicidal thoughts. You may have mood problems including depression (feeling hopeless or feeling bad about yourself), and thoughts of hurting yourself or suicide
  • Liver problems or worsening of liver problems, including liver failure. Symptoms may include nausea, loss of appetite, tiredness, dark colored urine and pale stools, yellowing of your skin or the white part of your eye, bleeding more easily than normal, confusion, and sleepiness. During your treatment with Rebif you will need to see your healthcare provider regularly and have regular blood tests to check for side effects
  • Serious allergic and skin reactions. Symptoms may include itching, swelling of your face, eyes, lips, tongue or throat, trouble breathing, anxiousness, feeling faint, skin rash, hives, sores in your mouth, or skin blisters and peels
  • Injection site problems. Symptoms at the injection site may include redness, pain, swelling, color changes (blue or black), and drainage of fluid
  • Blood problems. Rebif can affect your bone marrow and cause low red and white blood cell and platelet counts. In some people, these blood cell counts may fall to dangerously low levels. If your blood cell counts become very low, you can get infections and problems with bleeding and bruising. Your healthcare provider may ask you to have regular blood tests to check for blood problems
  • Seizures. Some people have had seizures while taking Rebif

Rebif will not cure your MS but may decrease the number of flare-ups of the disease and slow the occurrence of some of the physical disability that is common in people with MS.

Do not take Rebif if you are allergic to interferon beta, human albumin, or any of the ingredients in Rebif.

Before you take Rebif, tell your healthcare provider if you have or have had any of the following conditions:

  • mental illness, including depression and suicidal behavior
  • liver problems, bleeding problems or blood clots, low blood cell counts, seizures (epilepsy), or thyroid problems
  • you drink alcohol
  • you are pregnant or plan to become pregnant. It is not known if Rebif will harm your unborn baby. Tell your healthcare provider if you become pregnant during your treatment with Rebif
  • you are breastfeeding or plan to breastfeed. It is not known if Rebif passes into your breast milk. You and your healthcare provider should decide if you will use Rebif or breastfeed. You should not do both

Tell your healthcare provider about all medicines you take, including prescription and over-the-counter medicines, vitamins and herbal supplements.

The most common side effects of Rebif include:

  • flu-like symptoms. You may have flu-like symptoms when you first start taking Rebif. You may be able to manage these flu-like symptoms by taking over-the-counter pain and fever reducers. For many people, these symptoms lessen or go away over time. Symptoms may include muscle aches, fever, tiredness, and chills
  • stomach pain
  • change in liver blood tests

Tell your healthcare provider if you have any side effect that bothers you or that does not go away.

These are not all the possible side effects of Rebif. For more information, ask your healthcare provider or pharmacist.

Call your doctor for medical advice about side effects.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit or call 1-800-FDA-1088.

Refer to the Instructions for Use that comes with the Rebif® Rebidose® (interferon beta-1a) autoinjector.


Rebif is used to treat relapsing forms of MS to decrease the frequency of relapses and delay the occurrence of some of the physical disability that is common in people with MS.