Study shows Ig therapy is protective against measles

Immunoglobulin (Ig) replacement therapy offers protection against measles, according to a recent study that measured measles-neutralizing antibodies in patients with primary immunodeficiency (PI). The study is timely as measles cases grow in the U.S. due to decreasing vaccination rates and the virus proliferates abroad.

Through the study, researchers wanted to measure measles antibody levels in patients with PI who use Ig to determine if the present-day Ig products provide adequate levels of measles antibody. They asserted that a lack of data exists on trough (steady-state serum) levels of the measles antibodies in patients with PI treated with Ig.

Published in February 2025, the study measured measles antibody trough levels after intravenous immunoglobulin (IVIG) infusions in 33 adult patients and 15 pediatric patients at 16 infusion centers across the United States, the United Kingdom, and Hungary. Adult patients received five IVIG infusions of 10% IgG concentration and five IVIG infusions of 5% IgG concentration on either a 21-day or 28-day dosing regimen. The pediatric patients received five IVIG infusions of the 10% concentration.

Researchers found that both adult and pediatric patients had protective levels of measles-neutralizing antibodies. At the end of each five-week trial period, median trough levels were 1,300 milli-international units per liter (mIU/mL), well above the levels suggested by the FDA. With the decline in measles neutralis­ing antibody potency in the serum of the general population, a protective measles antibody level of ≥ 240 mIU/mL, which is double the protective level against measles in the healthy population (120 mIU/mL), has been suggested by the FDA for all Ig products.

The study used a product called Gammaplex, but the result would be the same with any product brand or route of administration, said Dr. Mark Ballow, a pediatric allergist-immunologist at the University of South Florida and Immune Deficiency Foundation (IDF) consulting medical director.

“If somebody has an adequate trough level, or steady-state serum IgG level, whether they are on IVIG or subcutaneous immunoglobulin (SCIG) replacement therapy, they should be protected,” said Ballow.

If a person is on IVIG every three to four weeks, said Ballow, they should use at least 530 milligrams per kilogram (mg/kg) of Ig to maintain protection against measles and a comparable dose with SCIG. Most of his patients are on 700-800 mg/kg, said Ballow.

“Patients should check to make sure they are on a dose that is 530 mg/kg, not only if they are exposed or in a high-risk situation, but regularly,” said Ballow. “So if their maintenance dose is 530 mg/kg, they should be protected. If they are on a lower dose than that, then they may want to consider boosting that dose, regardless of whether or not they are exposed."

According to the FDA, a dose of 530 mg/kg should provide a serum level of measles antibody of 240 mIU/ml for at least 22 days after the infusion for IVIG.

“Given the fact that we have measles and COVID still in the environment, and this is the worst influenza season, I think it’s prudent to have your patients at least on a maintenance dose of 530 milligrams per kg. However, some patients may require higher dosing to remain infection free or control chronic infection/inflammation like bronchiectasis.”

While Ig replacement therapy offers a level of protection, people with PI exposed to measles should contact their provider and receive an extra dose of Ig as soon as possible and within six days of exposure, according to FDA guidelines. A dose of 400 mg/kg provides a serum level of 240 mIU/mL for two weeks, which adds extra protection.

“Essentially, they’re saying that if a patient with an immune deficiency is exposed, then it may be prudent to add an extra dose of Ig replacement therapy just to be safe, whether on IVIG or SCIG,” said Ballow.

Those on IVIG who are traveling are advised to take an extra dose and wear a mask or time their dose so that they are at the optimal serum level. Patients on SCIG are at steady levels, so there’s no need for an extra dose or more precise timing, since they are getting weekly or biweekly dosing.

While Ig replacement therapy provides one layer of protection from measles, vaccines are another way to keep people with PI safe. Although people with PI on Ig do not benefit from getting a measles vaccine because the antibodies in the Ig neutralize the vaccine, they are most protected when the people around them, such as family and friends, have been fully vaccinated.

The CDC recommends two doses of measles, mumps, and rubella (MMR) vaccine; the first dose at 12 to 15 months of age, and the second dose at 4 to 6 years of age. Two doses of the vaccine are 97% effective at preventing measles.

Measles is highly contagious and 90% of unvaccinated people who come into contact with an infected person will contract the virus. Measles spreads through droplets in the air when someone breathes, coughs, or sneezes. Symptoms from the virus start with a runny nose, cough, high fever, and a rash. It can lead to severe health complications like pneumonia, brain inflammation, blindness, and seizures. Death occurs in 1 to 3 per 1,000 cases, and children 5 and younger and those with immunodeficiencies are at greater risk. A major cause of infant death from measles is measles virus-induced immunosuppression.

Because of the harmful effects of measles, building immunity through transmission instead of through a vaccine is not recommended. Ballow also cautions against non-vaccine remedies to treat or cure measles.

“Vitamin A deficiency among children in developing countries remains the leading cause of preventable severe visual impairment and blindness, and is a significant contributor to severe infections and death, particularly from diarrhea and measles. However, in this country, vitamin A deficiency is very rare. Thus, the use of vitamin A, or vitamin D, or cod liver oil as therapy to prevent or treat measles is folklore not based on science,” said Ballow.

Overdose on vitamin A and vitamin D is also possible, and cases of vitamin A toxicity have occurred in Texas, the center of the measles outbreak in the U.S.

The best course of action for a person with PI to cope with measles is to use the recommended dose of Ig replacement therapy and ensure that those they interact with face-to-face regularly are vaccinated.

“If there’s measles in their community, it’s probably a good idea to contact their clinical immunologist and come up with a plan, and discuss it with their families, as well,” said Ballow.