Adult Immunisation: The Evidence Behind the Guide

A 66-year-old retired bank manager from Udupi comes to the outpatient clinic with a cut on his shin from a garden tool. He has type 2 diabetes and COPD. The nurse has already drawn up an ampoule of tetanus toxoid, because that is what the clinic has always given. He mentions, on his way out, that he had a bad cough last monsoon and spent a week in hospital. This is an illustrative case, not a real patient.

By the end of this article you will know what should be in that syringe instead. You will also know which other vaccines this man is due, and why an adult needs them at all.

1. The Syringe in the Nurse’s Hand: Td, Not TT

“Tetanus toxoid has worked for decades. Why change it?” Because tetanus is not the only thing it should prevent. Adult immunity against diphtheria wanes, and what protection remains rests on herd immunity. So the Government of India replaced TT with Td (Tetanus and adult-dose Diphtheria) in the National Immunisation Schedule in 2018-19.

In India, there is a widespread unsafe practice of prescribing standalone Tetanus Toxoid (TT) for wound management or during pregnancy. The tool’s instruction is short: prescribe Td or Tdap. Never standalone TT. Whether this wound also needs tetanus immunoglobulin is a separate decision, made in the tetanus pathway.

2. Why Vaccinate an Adult at All?

Most of us think of vaccines as something for children. Our patient probably thinks so too. The tool used to answer that in its Evidence tab, as its section 3:

3. Why Adult Immunisation Matters in India

• Immunosenescence: Innate and adaptive immune function declines with age. That raises both the susceptibility of older adults to influenza, pneumococcal disease and herpes zoster, and the mortality once they have them.
• Comorbidity Burden: Diabetes, CKD and COPD are all rising in India, and each leaves a patient less able to withstand a respiratory infection. For those patients vaccination is part of treating the underlying condition.
• AMR Stewardship: Viral vaccines (like Influenza) prevent secondary bacterial pneumonias, directly reducing unnecessary empirical broad-spectrum antibiotic prescriptions.

Take the first word slowly. Immunosenescence means the ageing of the immune system. Both arms of it, the quick innate response and the slower adaptive one, lose strength with the years. An older adult catches influenza more easily, and is more likely to die of it.

Now put our patient against the three points. He is 66, so the first applies. He has diabetes and COPD, so the second applies twice. And his week in hospital last monsoon may well have been influenza followed by a bacterial pneumonia. It was probably treated with exactly the broad-spectrum antibiotics the third point is about. Every one of the three reasons is sitting in front of you.

3. Pneumococcal Vaccine: One Dose Now

You may have learnt a two-step pneumococcal series: a conjugate vaccine, then a year’s wait, then the polysaccharide vaccine. The Association of Physicians of India changed that in 2026. PCV20 is now the preferred single-dose pneumococcal vaccine. It covers 7 additional serotypes compared to PCV13, so the older, sequential PCV13, then a year’s wait, then PPSV23 approach is no longer needed. That approach suffered from high drop-out rates and polysaccharide-induced hyporesponsiveness.

“Can I give both on the same day, to save him a visit?” No. Never give PCV and PPSV23 at the same time. ACIP’s stated reason is that co-administration studies found a lower antibody response than when the two are spaced. If the older series is used, the tool sets out the spacing.

4. Shingles: The Recombinant Vaccine

There are two zoster vaccines in the literature, and only one belongs in your prescription:

Our patient is over 50, so RZV is due: two doses, 2 to 6 months apart.

5. The Live Vaccines, and Who Must Not Have Them

A live attenuated vaccine can replicate in a host who cannot contain it. That is why live vaccines are strictly contraindicated in pregnant women, where the organism can cross the placenta, and in severely immunocompromised patients. The tool carries a mnemonic for them: “Be A VIP, MMR!” BCG, Adenovirus (oral), Varicella, Influenza (the intranasal LAIV only), Polio (the oral OPV), and Measles, Mumps, Rubella. Yellow fever and the old live zoster vaccine belong to the same family.

Notice that the influenza vaccine we give adults by injection is inactivated. It is the intranasal one that is live.

6. The Common Mistake

The common mistake is the one the nurse was about to make: standalone TT, given because it is what the clinic has always stocked. It is easy to see why. TT is familiar, and it is what the cupboard has held for years. But it leaves the adult without diphtheria protection, and Td protects against both. A close second is to treat a wound and send the patient home without asking about any other vaccine. A wound visit is often the only time an adult with diabetes sits in front of you without a complaint of his own.

Back to Our Patient

The TT goes back on the tray. He receives Td for the wound, after the tetanus pathway has decided on immunoglobulin. For a man of 66 with diabetes and COPD, the tool’s result lists three more. Influenza vaccine once a year before the monsoon, PCV20 as a single dose, and RZV in two doses. He leaves with the first of them given and the dates of the rest written down.

Try This

His daughter-in-law is 30 weeks pregnant. She asks which vaccines she should have, and whether the MMR she missed as a child can be given now. Illustrative case.

Answer. Tdap now, because it is given at 27 to 36 weeks in each pregnancy, so that the baby is born with her antibodies against pertussis. Inactivated influenza, in any trimester. Not MMR: live vaccines are contraindicated in pregnancy, and she should wait at least 4 weeks after a live vaccine before conceiving again. HPV is deferred until after delivery; if a dose was given before the pregnancy was known, no action is needed.

Take-Home Points

• For a wound or a pregnancy, prescribe Td or Tdap. Never standalone TT.
• Ageing immunity, diabetes, CKD and COPD are each a reason to vaccinate an adult.
• PCV20 is the preferred single-dose pneumococcal vaccine; never give PCV and PPSV23 together.
• RZV is the zoster vaccine for every adult of 50 and over; the live ZVL is obsolete.
• No live vaccine in pregnancy or severe immunosuppression: remember “Be A VIP, MMR!”

For patients who ask whether vaccines are safe at all, the author’s article Doctor, Are Vaccines Really Safe? answers in plain words. The HPV vaccine has its own pathway and its own article.

Declaration: the author built and maintains the tool. It is free to use. The figures in this article are those the tool carried in its Evidence tab on 5 November 2026, each from the source the tool names. The illustrative cases follow the tool’s rules; check the tool’s result for a real patient.

References

1. Association of Physicians of India (API). Indian Consensus Guidelines on Adult Immunization, 2026 Update. API; 2026.
2. Dhawan AM, Desai A, Gvalani A, Anand S, Das P. A comprehensive review of the latest Indian guidelines on adult immunization. Int J Community Med Public Health. 2025;12(2):1159-1165.
3. Centers for Disease Control and Prevention (CDC). Adult Immunization Schedule by Age. ACIP; Updated 2026.
4. Giriappa B, Choraria N, Ponce P, et al. Immunogenicity and safety of 20-valent PCV (PCV20) in adults ≥18 y of age in India. Hum Vaccin Immunother. 2026;22(1):2605847.
5. World Health Organization. WHO Recommendations for Routine Immunization: Summary Tables. Geneva: WHO; 2023.