Some 250 immigrant children at a Texas detention facility were given adult doses of a hepatitis A vaccine, when the prescribed amount for adults is about twice the amount typically prescribed for children.

It’s not certain why the children received double the amount of the vaccine they should have been prescribed, though the U.S. Immigration and Customs Enforcement (ICE) claims that none of the kids have been hospitalized or have had any side effects. The detention facility is located at the South Texas Family Residential Center in Dilley, which holds some 2,000 women and children from Central America who had entered the U.S. through Mexico seeking asylum.

ICE claims that there will likely be little to no side effects of the vaccine — even though it was the wrong amount. If anything, the officials said, it might cause a stronger immune response, according to the AP.

“Parents at the facility were advised and counseled by medical professionals about potential side effects, with services made available in multiple languages,” Richard Rocha, ICE spokesman, said in a statement.

But immigration advocates believe this mistake is yet another example of poor health care given to immigrants in detention facilities. “Volunteer attorneys at Dilley, as well as those at similar detention centers in Karnes, TX, Berks, PA and the previous facility in Artesia, NM, have long noted disturbing patterns of what appears to be inadequate health care for the women and children,” Crystal Williams, executive director of the American Immigration Lawyers Association, said in a statement. “This latest permutation is beyond appalling — it is putting children at risk not just for short-term reactions but for unknown long-term risks.”

Hepatitis A is a contagious liver infection caused by the hepatitis A virus. Contaminated food or water, or close contact with an infected person, can get you sick with the virus. The vaccine is recommended by the CDC for all children at about age 1, though the doses prescribed to babies are different than those prescribed to adults.

Here’s why it’s important that age is taken into consideration when it comes to vaccination doses: There’s often a specific time period when it’s best to give infants or young children vaccines. For example, for quite some time the World Health Organization (WHO) recommended that rotavirus vaccines be given to children at age 6 to 15 weeks, and the maximum age for the last dose of the vaccine should be 32 weeks. There is some flexibility with the age restriction for the rotavirus vaccine, especially since many kids in developing countries don’t have access to the vaccine that early in life — or specifically between 6 to 35 weeks. Even though getting the vaccine outside of that 6- to 32-week time frame creates a higher risk of intussusception — one section of the intestine sliding into another — WHO health officials deemed the risks smaller than the benefits of extending the age restriction.

The CDC has recommendations for other types of vaccines, including diphtheria, Hepatitis B, HPV, flu, and measles-mumps-rubella (MMR). In general, these guidelines are in place to ensure the vaccine works most effectively and with the least side effects. Adults have different guidelines, doses, and intervals between doses than children.

In the case of the immigrant children receiving adult doses, while many side effects will likely not occur, it’s important to remember that these guidelines are in place for a reason.