The last Americans to get the vaccine against the coronaviruses are children younger than 5 years old.

Since the beginning of the Pandemic, parents of young children have faced almost impossible choices because of the lack of vaccines. Many children were deprived of normal childhood experiences because they were kept out of school. All that can change now.

The CDC recommended the Moderna and Pfizer-bioNTech vaccines for children as young as 6 months. The shots will be given to the young children for the first time.

A mother of two in Oxford, Miss., said she has been waiting for her two-year-old daughter to qualify for the vaccine since she got her first shot at the age of five.

Yes! She said they would like to be first in line.

According to a recent Kaiser Health poll, only one in five parents will get their kids vaccinations immediately. Many people are planning to hold off.

The C.D.C.'s decision puts parents of young children on the spot as Americans consider the risks of living with the swine flu.

Vaccines still offer protection against illness and death, even though they have lost some of their effectiveness. Many people thought the battle was over because huge numbers of Americans were infectious.

There is a lack of enthusiasm. Richardson said he didn't want his children to be exposed to vaccine because of the constant changes to the number of shots recommended.

He said that the first shot was a booster and the second was a booster.

After navigating the perils of the Pandemic with their children, parents now face new questions that have stumped regulators and experts. Which vaccine is more effective? Will they work, and how long will it take? Most of the young children have already been exposed to the virus.

ImageFor young children, states have so far ordered 2.5 million doses of the Pfizer-BioNTech vaccine and 1.3 million doses of the Moderna vaccine.
For young children, states have so far ordered 2.5 million doses of the Pfizer-BioNTech vaccine and 1.3 million doses of the Moderna vaccine.Credit...Karsten Moran for The New York Times
For young children, states have so far ordered 2.5 million doses of the Pfizer-BioNTech vaccine and 1.3 million doses of the Moderna vaccine.

The Pfizer-BioNTech and Moderna shots are considered safe for young children, and both give the same levels of protection as those seen in young adults. In the early days of the Pandemic, the adult vaccines gave amazing protection.

Moderna's vaccine seems to produce a strong immune response in young children, and it protects them within 42 days after the first dose. Less providers are likely to offer it as an option over Pfizer's vaccine because it causes one in five children to get a fever.

Children will need to get three doses of the Pfizer-BioNTech vaccine in order to be protected from the disease. The effect may last longer compared to Moderna's regimen.

Jetelina is a public health expert and author of the widely read newsletter, "Your Local Epidemiologist."

She said that there would have to be a lot of communication about the difference between the two.

Some answers to parents might be provided by a head-to-head comparison of the two vaccines, according to experts. There are a lot of differences in the way the vaccines were formulated.

It will be hard to say one is better than the other, according to William Towner, who led vaccine trials for both Moderna and Pfizer.

He said that the choice may depend on whether parents are willing to go for three or two shots.

Moderna has only been used by Pfizer- BioNTech vaccine, which many providers are unfamiliar with. Americans have received about 350 million doses of that vaccine, which is less than the Moderna vaccine and the Johnson & Johnson vaccine.

The Pfizer vaccine and the Moderna vaccine have been ordered by many states. There are 18 million children in this age group.

Older children have had slow uptake. Less than 30 percent of children in the age group of 5 to 11 years old have received two shots of the Pfizer-BioNTech vaccine.

The vaccines have proved to be very safe, but a lot of parents are hesitant about them. Some people are wary because the vaccines are new or because they think the risk is small for their children.

75 percent of the children were thought to have been exposed to the disease. C.D.C. scientists noted on Saturday that vaccinations provide more powerful and consistent protection even if a child has already been exposed.

Some parents have moved on from the swine flu.

Some parents in Ohio were more concerned with staying cool during the summer heat wave than with the risk of the coronaviruses. She said she did not intend to immunize her two daughters.

She said that life was back to normal.

Williams said she wasn't sure if she would be able to give her children the vaccine. If it were necessary, Ms. Williams would get it for them.

ImageSimone Williams, a mother in Middletown, Ohio, with her 1-year-old twins, Caidon and Arissa.
Simone Williams, a mother in Middletown, Ohio, with her 1-year-old twins, Caidon and Arissa. Credit...Maddie McGarvey for The New York Times
Simone Williams, a mother in Middletown, Ohio, with her 1-year-old twins, Caidon and Arissa.

The merits of the vaccine were going to be explained by some doctors. In parts of the country, even routine immunizations are fraught with controversy.

Lindsey Douglas is the medical director of quality and safety at the Mount Sinai Kravis Children's Hospital.

There is more information available in the last two and a half years. There is more misinformation out there as well.

The chances of the vaccines being used in the youngest children were not good.

The Moderna and Pfizer-BioNTech vaccines offered estimates of efficacy that were far beyond expectations.

The vaccine was gradually being tested in younger children, but each new form of the virus was more difficult to understand.

The newer versions of the Omicron variant have evolved to partially dodge not just the two-year-old vaccines, but even the immunity produced by an infection with the form of Omicron that was circulating just a few months ago.

The efficacy estimates for adults were in the 90's. Fifty-one percent for two doses of Moderna's vaccine in children 6 to 23 months, and forty-seven percent for children 2 to 5 years old.

The vaccine did not meet the FDA's bar for an immune response, justifying the agency's delay in evaluating the vaccine.

It is unacceptable that it has taken so long for our kids to get the vaccine. I know how important it is to do clinical trials rigorously and find the right dose.

The F.D.A. has authorized two and three doses of the Moderna vaccine for young children.

Children will need a third dose of Moderna and a fourth of Pfizer if officials determine that they need booster shots.

Pfizer has estimated an efficacy of 80 percent for three doses of its vaccine. The C.D.C.'s advisers noted at a meeting on Friday that the calculation was based on three children in the vaccine group and seven placebo recipients.

Sarah Long is an infectious diseases expert at the college of medicine. She said she was comfortable with the data supporting the vaccine's effectiveness.

If the Covid vaccine can be offered alongside other immunizations, parents of the youngest children may be more willing to give it a try. Dr. Towner predicted that more parents would choose Moderna over the other vaccine.

He said that it may be difficult for some parents to do more than one dose. Some parents may decide to go to the Moderna if they have a choice.

ImageBrendan Kennealy, a father of two, plans to vaccinate his children.
Brendan Kennealy, a father of two, plans to vaccinate his children.Credit...Jenn Ackerman for The New York Times
Brendan Kennealy, a father of two, plans to vaccinate his children.

Parents don't need to convince them. She said the news was life-changing because her family has been living in a sort of isolated reality. She plans to take Sophia to a museum and open a bottle of champagne after she gets her vaccine.

Brendan Kennealy said after his daughters, 4-year-old Hazel and 1-year-old Ivy, are vaccinations, he and his wife would drive them up to the lake town of Duluth, where they would try new restaurants.

His mother is vulnerable to severe Covid and the family has avoided spending time indoors. His children stopped swimming and gave up gymnastics.

The F.D.A. halted progress on vaccines for children after Mr. Kennealy got very, very happy.

He said that the shocks of hope were unnecessary. I am trying to keep that from happening until we take them to the Walgreens or wherever.

Adam Bednar from Baltimore was one of the contributors.