CBC Radio - The 4th doses of vaccines are coming

"The data clearly shows that for older people and those who have immunocompromised systems, the additional doses can be really helpful. Especially given that our natural immunity to the vaccine starts to wane after about three months, more so with these individuals with weakened immune systems. That's why it is recommended for these populations to be given an earlier booster dose than other populations," says Dr. Samir Sinha, NIA Director of Health Policy Research.