TDaP booster needs to be done every 10 years anyway. That’s the booster for tetanus, diphtheria, and pertussis (whooping cough). It’s also recommended when pregnant, working in childcare or teaching especially around infants, when an infant is born into the family and you will be around the child before it can be immunized, and if you have potential tetanus exposure and don’t know when you were last vaccinated. The guidelines for the Shingrix vaccine is to give the first dose at around age 50 and give the second dose 2-6 months later. Most likely you caught chickenpox when you were a child and you never clear the varicella-zoster virus. It just goes dormant in your dorsal root ganglia where it can later reactivate, typically during times of stress, if immunocompromised, or as your immune system starts to decline as you get older. When this happens, it follows those nerve pathways, hence the typical shingles rash pattern. Getting the Shingrix vaccine earlier starting at age 50 is associated with higher rates of efficacy but it’s still much more effective than the previous shingles vaccine, Zostavax, regardless of what age you are when you get it. When your dr does titers for antibodies, they are specific to the type of antibody so they don’t test for all of them. FYI, you might be due for pneumococcal vaccination too if your vaccination history is unknown or if you have certain medical conditions or are immunocompromised.