Our 4-month-old was born early and gets

Tomorrow morning's shot is the right call, and it does not need anything clever from you tonight — just the record, the routine, and a written plan for who calls whom if he turns feverish overnight.

1) What you have already tried, and the better next step

Asking the nurse line was right — keep it, and use it for one thing it is good at: *this child's* plan. Two asks worth making before Tuesday:

• "Please write down, on the leaflet they hand me, exactly which symptoms mean we call back tonight and which number we call."
• "Is there a comfort plan you want us to follow for the first day, on the label you give us?" — that instruction comes with a dose, and I will not write one for you. Follow what is printed on what the clinic gives you, or what the nurse tells you on the phone.

Better alternatives to anything you might be planning tonight:

• Put the three questions in writing now, so Tuesday takes 60 seconds, not 20 minutes of a tired brain. Screenshot this:

1. "He was born early — does that change anything about the plan, and what is his corrected age for this visit?"
2. "What is due at this visit, and does this antibody replace anything else on his chart, or sit alongside it?"
3. "What would make us come back tonight, and who do we call first — you, or the emergency number?"

• Line up the paperwork tonight: his vaccine record, any previous reaction to any injection, and whether he is currently well. A mild cold or a snuffle is not a reason to cancel — go and let the vaccinator decide. A real fever or a baby who is clearly unwell is a reason to phone them in the morning and ask before you travel.
• Decide the overnight role now, while you are calm. School week is the hard part. Write one line on the fridge: *if his temperature is up and he is not himself — who calls, and who takes him.* One adult, one job.

2) How it protects him, and what it does not replace

• It is an antibody, not a vaccine — ready-made protection he receives directly. It starts working right away, which is the point for a 4-month-old.
• The American Academy of Pediatrics' parent page (checked 5 Oct 2026) says these antibodies last at least 5 months and the shot is up to 90% effective at preventing infants being hospitalised with RSV. It lowers the risk of serious illness; it does not promise he never catches RSV.
• It does not replace the rest of his routine vaccines, and it is not a substitute for hand-washing. RSV spreads through close contact, through surfaces, and through cough or sneeze droplets. The same AAP page lists staying away from crowded indoor spaces and washing hands as the other layers.
• Season timing is local. RSV is most common late autumn to early spring in most places, but the AAP page says timing differs by region — your clinic confirming Tuesday is the right place to confirm, not a general calendar.

3) The caregiver rules for this week

Do (routines, nothing you have to buy):

• A wash-hands-and-change rule at the door. The sibling comes home from school, the elder visits — hands washed before anyone holds him. Twenty seconds, at the door, every time. This is the single highest-value thing in the house this season.
• Light clothing, a warm but ventilated room, keep offering feeds. For a 4-month-old, feeds and wet nappies are your real dashboard.
• Use the thermometer for a trend, not a verdict. Write the number and the time. Never use one reading to decide "we can stay home" — appearance and behaviour decide that.
• Stay for the observation time the clinic asks for after the shot, if they are still on site. Tuesday morning, that is the cheapest safety in the whole plan.

Avoid:

• Do not cancel Tuesday over a snuffle, and do not assume a temperature afterwards proves the vaccine "did something bad."
• Do not give any fever medicine or comfort medicine that the clinic has not told you to use, and do not alternate two of them. Any dose comes from the clinic's own label or the nurse on the phone, not from me.
• No leftover antibiotics, no "just in case" powders, nothing bought online. Nothing to be given at home for a reaction.
• Do not use alcohol wipes on his skin to cool him, and no cold bath — a cool bath slightly cooler than him, or a cool cloth, is the only cooling I would suggest.
• Do not kiss his face / hands-to-face when anyone in the house has a cold this week; hands, not face.

4) Red flags — when to stop DIY and get help

Call your local emergency number now, and do not wait to see if it settles:

• Swelling of the tongue or throat, widespread hives, wheeze, or collapse — in the minutes after a shot, or any time in the first day.
• Fast or hard breathing, grunting, ribs sucking in, or blue lips.
• A fit, or he will not wake properly.
• A rash that does not fade when you press a clear glass firmly against it.
• He will not drink or breastfeed at all, or you cannot rouse him.
• He is floppy, pale and mottled, has a weak or moaning cry, or is simply "not him" and you cannot console him.

Phone the clinic or the nurse line the same day if: he is feeding less and passing fewer wet nappies than usual, is feverish and fretful for more than a day without settling, or the injection site is red, hot or swelling wider over the following day.

At this age, a low temperature or an unstable temperature can itself be the sign — do not wait for a fever to appear before seeking care, and do not accept "it's just a cold" as the explanation for a baby who looks unwell.

One practical note for the school week: if he becomes unwell in the night, take the temperature and the time, keep him warm, note the last feed and last wet nappy, and take the vaccine record with you. That is the whole sheet.

What "success" looks like in the next 24 hours

Not "no symptoms" — a fussy, warm, slightly sore-thighed baby who is still feeding, still wet, still waking, and still himself by tomorrow evening is the expected, ordinary picture. Success is: the appointment happened, the record went with you, you came home with a written list of what to watch, and nobody in the house was guessing at a dose at 2 a.m.

One thing I could not confirm

Which country or city you are in. RSV season timing and the local programme's own leaflet are region-specific, and I will not guess a country from your language. Tell me the city and I can point you at the official RSV page for your area before Tuesday.