What happens, and when

The NHS schedule for babies under one year is short and front-loaded:

8 weeks: 6-in-1 vaccine (1st dose), rotavirus vaccine (1st dose), MenB vaccine (1st dose)
12 weeks: 6-in-1 (2nd dose), MenB (2nd dose), rotavirus (2nd dose)
16 weeks: 6-in-1 (3rd dose), pneumococcal vaccine (1st dose)

Then, in the second year:

1 year: MMRV vaccine (1st dose, for children born on or after 1 January 2025), pneumococcal (2nd dose), MenB (3rd dose)
18 months: 6-in-1 (4th dose, for children born on or after 1 July 2024) and an MMRV dose

The 6-in-1 does the heavy lifting. The NHS says it "protects children against 6 serious illnesses": diphtheria, hepatitis B, Hib (Haemophilus influenzae type b), polio, tetanus and whooping cough. Most of the doses are injections; the rotavirus vaccine is given as drops into the mouth.

If you are reading from outside the UK

Schedules differ by country and the differences are real, not cosmetic. The CDC's schedule for the United States starts hepatitis B at birth, gives DTaP, Hib, polio, pneumococcal and rotavirus at 2, 4 and 6 months, adds flu and COVID vaccines from 6 months, and gives MMR, varicella and hepatitis A between 12 and 18 months, with an RSV antibody depending on the mother's RSV vaccine status and the child's health. Follow the schedule where you live.

Why so many at once

The AAP addresses the question head on: "We know from decades of research that the vaccines work best at these ages, and with this spacing between doses", and "the pace has a purpose: to keep your child healthy and active". On combination vaccines like the 6-in-1: "Combining protection in one shot means fewer needle sticks. Your child's immune system is protected from multiple diseases at once."

What normally happens afterwards

The NHS lists the common side effects of the 6-in-1: swelling or pain where the injection was given, a high temperature, feeling tired, loss of appetite, being sick or diarrhoea, and irritability. All of those are the immune system responding, and all of them are expected rather than alarming.

Practically, that often looks like a grumpy afternoon, a hot and unsettled evening, a leg that is tender to touch for a day or two, and a longer or more broken night. Extra feeds and extra cuddles are the whole treatment for most babies. The NHS says children's paracetamol can be given to ease symptoms — check the packaging for suitability, or speak to a pharmacist or doctor.

Serious reactions

The NHS: "More serious side effects such as a severe allergic reaction (anaphylaxis) are very rare and usually happen within minutes. The person who vaccinates your child will be trained to deal with allergic reactions and treat them immediately." That is the practical reason the rare risk is manageable — the timing means it almost always happens while you are still in the room with someone trained to treat it.

What is not a normal reaction

A raised temperature after vaccination is expected. A temperature that crosses the NHS's urgent thresholds is not something to attribute to the vaccine and wait out. Ask for an urgent GP appointment or call 111 if your child is under 3 months old with a temperature of 38C or higher, is 3 to 6 months old with a temperature of 39C or higher, or is unwell and you are worried about them.

The NHS's general fever guidance also applies: call 999 for a stiff neck, a rash that does not fade when pressed with a glass, a first febrile seizure, unusually cold hands and feet, blue, grey, pale or blotchy skin, drowsiness that is hard to rouse, extreme agitation, or difficulty breathing.

Who cannot have the vaccine, and when to postpone

The NHS says most children can have the 6-in-1. The exceptions are a previous serious allergic reaction to a dose of the vaccine, or to anything in it including neomycin, polymyxin, formaldehyde or polysorbate 80. If your child has a condition affecting their brain, such as epilepsy, speak to a doctor, nurse or health visitor first.

On timing: "If your child has a high temperature, wait until they're feeling better before having the vaccine. If they are unwell but do not have a high temperature, check with a doctor, nurse or health visitor if they can still have the vaccine." A cold with no fever is usually not a reason to postpone.

Missed appointments

Missing a date is recoverable. The NHS: "It's best to have vaccines on time, but you can still catch up on most vaccines if you miss them." For the 6-in-1 specifically, children can still have it up to the age of ten. Contact your GP surgery to book or rearrange.

Making the appointment easier

Feed before or during, if you can. Bring a comfort item. Dress your baby in clothes that give quick access to the thighs. Hold them chest-to-chest rather than laying them down. Expect a short, loud protest and a fast recovery — most babies settle within minutes. And plan a quiet rest of the day rather than a busy one.

Why it belongs in the sleep-safety conversation too

The NHS's guidance on reducing the risk of sudden infant death syndrome includes, among its "do" list: "make sure your baby is up to date with their routine NHS vaccinations – these provide protection against childhood illnesses that may increase the risk of SIDS."

When to speak to a health visitor or doctor

Speak to your GP surgery if you have not been contacted about your baby's vaccinations, if you are not sure which doses they have had, if your child is unwell and due a vaccine, or if you need to change an appointment. Contact 111 or your GP urgently for the fever thresholds above, or if your baby is unusually drowsy, floppy, or has swelling that is spreading and getting worse rather than settling over a couple of days.

Baby Vaccinations