First of all, the COVID vaccine at this point is not recommended for children under 12
Everyone already knew this, and I'm fairly sure GK was not suggesting vaccinations for children until testing is completed.
Second, we don't know the long term effects from it.
Name a vaccine for which we knew the long term effects in advance of administering the vaccine.
Third, it is still not fully FDA approved.
Neither was the first smallpox vaccine. The FDA didn't exist then.
Finally, Covid does not appear to cause many issues in 4 year olds
While all children are capable of getting the virus that causes COVID-19, they don't become sick as often as adults. Most children have mild symptoms or no symptoms.
According to the American Academy of Pediatrics and the Children's Hospital Association, in the U.S. children represent about 13% of all COVID-19 cases. Research suggests that children younger than ages 10 to 14 are less likely to become infected with the virus that causes COVID-19 compared to people age 20 and older.
However, some children become severely ill with COVID-19. They might need to be hospitalized, treated in the intensive care unit or placed on a ventilator to help them breathe, according to the Centers for Disease Control and Prevention (CDC).
In addition, children with underlying conditions, such as obesity, diabetes and asthma, might be at higher risk of serious illness with COVID-19. Children who have congenital heart disease, genetic conditions or conditions affecting the nervous system or metabolism also might be at higher risk of serious illness with COVID-19.
Research also suggests disproportionately higher rates of COVID-19 in Hispanic and non-Hispanic Black children than in non-Hispanic white children.
Rarely, some children might also develop a serious condition that appears to be linked to COVID-19.
We don't have all the data on how it effects 4 year olds.
See above.