IT'S BEEN A LONG, aggravating road for guardians of toddlers and threenagers hoping to get their kids the Covid vaccine, but the end is finally in sight.

Advisers for the Food and Drug Administration unanimously voted in favor of authorizing Pfizer's Covid vaccine for kids six months to four years old and Moderna's vaccine for kids six months to five years, and the Centers for Disease Control followed soon after. Here's what to know about these shots for the youngest among us.

When will kids under five be able to get the Covid vaccine?

Right now. Shots are already being shipped out to pharmacies and hospitals, and Seattle Children's has opened appointments for this age group.

How effective is the Covid vaccine for kids under five?

Pfizer's vaccine for this age group is just three micrograms, or a 1oth of the adult doses, and is a three-dose series. The first two shots are spaced three weeks apart, with the third coming two months later. According to the data Pfizer submitted to the FDA, their vaccine is 80 percent effective seven days after the third dose—but that was based on a very small number of cases as not all children in their clinical trials had yet received the third dose. After two doses, Pfizer's efficacy is just 28.3 percent.

Moderna's vaccine involves two doses of 25 micrograms each for children, or a quarter of the adult 100-microgram shots. Shots are given four weeks apart. Moderna doses do stimulate a "robust neutralizing antibody response" in the youngest age group, and its ability to prevent symptomatic infection in the first place was 51 percent in those six months to two years and 37 percent in those two to six.

Which Covid vaccine is better for kids under five?

That depends on what you're looking for. Data presented during the FDA panel meeting shows that Moderna's two-dose vaccine is less effective at preventing Covid than Pfizer's vaccine three-dose series, but remember, Pfizer's data is based on a small number of cases. If you're comparing just two doses against two doses, Moderna wins.

On the other hand, Pfizer's vaccine seems to cause fewer side effects, such as fever, than Moderna's vaccine.

The third thing to consider is timing: Moderna's vaccine is only two doses, offering full protection to children within six weeks, whereas Pfizer's is three shots and would take 12 weeks for children to be fully vaccinated.

Will there be huge demand here once a Covid shot is authorized for kids under five?

It seems that way. After Children's opened its vaccine appointments, slots were quickly booked up after a few hours. The wait, at least right now, is more than a month out. This will likely ease as more health care organizations offer appointments and supply increases.

Where can I get a vax appointment for my kid?

Mad rush or not, the best place to start is your pediatrician, who has experience administering shots to this age group. Local pharmacies may also offer appointments, as well as hospital- or county-run vaccination sites and Seattle Children's. Be sure to check for age restrictions before you make an appointment as some mass-vaccination sites or pharmacies do not administer shots to young children.