(CNN) —  

A Republican senator forcefully defended mandatory vaccinations Tuesday after his Republican colleague, Sen. Rand Paul, blasted national vaccination requirements as a danger to liberty.

Sen. Bill Cassidy, of Louisiana, said vaccines are a key public health safeguard after Paul, of Kentucky, criticized mandatory vaccinations, despite saying that he and his children had been vaccinated. The comments from the senators, both of whom are doctors, come after more than 200 measles cases have been reported across 11 states and prompted Washington state Gov. Jay Inslee to declare a state of emergency in January.

“As we contemplate forcing parents to choose this or that vaccine, I think it’s important to remember that force is not consistent with the American story, nor is force consistent with the liberty our forefathers sought when they came to America,” said Paul, an ophthalmologist, during a Senate Health, Education, Labor and Pensions Committee hearing advocating the use of vaccines.

“I don’t think you have to have one or the other, though,” he added. “I’m not here to say don’t vaccinate your kids. If this hearing is for persuasion, I’m all for the persuasion – I’ve vaccinated myself, I’ve vaccinated my kids. For myself and my children I believe that the benefits of vaccines greatly outweigh the risks, but I still do not favor giving up on liberty for a false sense of security.”

Addressing criticism that parents who refuse to vaccinate their children endanger those with immune deficiencies, “there doesn’t seem to be enough evidence of this happening to be recorded as a statistic, but it could happen,” Paul said. “But if the fear of this is valid, are we to find that next we’ll be mandating flu vaccines,” he said, citing scientists’ “educated guessing” on what flu strain to put in the next year’s vaccine.

Paul also alleged that “no informed consent is used or required when you vaccinate your child.”

Cassidy, a gastroenterologist, fired back during his testimony, arguing that those exercising their liberty to not get vaccinated should pay the price of not being allowed to expose others and potentially put them at risk.

“The requirement is just that you cannot enter school unless you’re vaccinated,” Cassidy said. “Now, if you’re such a believer in liberty that you do not wish to be vaccinated, then there should be a consequence, and that is that you cannot infect other people.”

“If you believe in liberty, that’s fine, don’t get immunized. But I don’t think you need to necessarily expose others to disease,” he added.

The Louisiana Republican lamented patients who needed liver transplants or suffered from terrible diseases simply because “they just, for whatever reason, didn’t understand vaccination was important.”

He cited how many hospitals require that their employees be vaccinated “because they understand that herd immunity is important” and that a nurse who has not been vaccinated “can be a Typhoid Mary, if you will, bringing disease to many who are immunocompromised.”

Cassidy also pushed back on Paul’s comments on the flu vaccine – arguing that flu shots mitigate the severity of outbreaks despite not addressing all strains of the virus – and Paul’s assertion that vaccines do not require consent forms.

“There is a federal statute requiring that vaccine information statements should be given. That is a federal requirement,” he said. “And in the name of liberty we should rely therefore upon states and localities to make a further requirement, but they typically do require an informed consent. So that’s important to know, not to be misled by … not to be misled regarding that.”