Let's talk vaccines: ᴼⁿᵉ ˢʰᵒᵗ, ᵐᵘˡᵗⁱᵖˡᵉ ᵈᵒˢᵉˢ, ᵃⁿᵈ ᵇᵒᵒˢᵗᵉʳˢ

So, what's up with the multiple doses and/or booster shots needed? It depends on the disease, the kind of vaccine, and the kind of antibodies created.

Let's first look at the reasons why we might need to receive multiple doses of a vaccine.

▪️For some vaccines (primarily inactivated vaccines), the first dose does not provide as much immunity as possible. So, more than one dose is needed to build more complete immunity. The vaccine that protects against the bacteria Hib, which causes meningitis, is a good example.

▪️For some vaccines (primarily live vaccines), studies have shown that more than one dose is needed for everyone to develop the best immune response. For example, after one dose of the MMR vaccine, some people may not develop enough antibodies to fight off infection. The second dose helps make sure that almost everyone is protected.

▪️In the case of flu vaccines, adults and children (6 months and older) need to get a dose every year because the flu viruses causing disease may be different from season to season. Every year, flu vaccines are made to protect against the viruses that research suggests will be most common. This is the only vaccine, to date, that needs to be received every year to be effective. In fact, to date, this is the only disease that mutates as often as it does. (To date is used because it is still undetermined whether or not the COVID-19 disease will behave in the same way or not.)

Now what about those booster shots?

For some vaccines, after a while, immunity begins to wear off. At that point, a “booster” dose is needed to bring immunity levels back up. For example, in the case of the DTaP vaccine, which protects against diphtheria, tetanus and pertussis, the initial series of four shots that children receive as part of their infant immunizations helps build immunity. But a booster dose is needed at 4-6 years old. Another booster against these diseases is needed at 11-12 years of age. This booster for older children—and teens and adults, too—is called Tdap.

A booster dose serves as a reminder to the immune system. It says, "Hey, remember me? I'm still a potential threat so keep making those antibodies against me!"

{You can find all the sources I used by clicking here.}