First Kitten Vaccination: The 8-16 Week Cattery Schedule

First vaccination is a calendar problem, not a shopping problem. Start the core series at 8 weeks, repeat at 3 to 4 week intervals until 16 weeks, and keep the litter on site until 7 days after the final dose. The number that drives every other decision is 3: colostral antibody falls by roughly half every 3 weeks, which opens a gap between 6 and 14 weeks when a kitten can look protected and be unprotected at the same time.

What maternal antibody actually does

A kitten is born with almost no antibody of its own. It absorbs colostrum in the first 12 to 16 hours, and by about 24 hours the gut has closed and nothing more crosses. From then on the antibody it received decays with a half-life of roughly 3 weeks: near 100% in the first days, about 50% at 3 weeks, 25% at 6 weeks, 12% at 9 weeks and 6% at 12 weeks. Protective levels are usually gone between 8 and 12 weeks in a kitten that nursed well, and as early as 6 weeks in one that did not get 12 good hours of colostrum.

That curve is why a single early shot is unreliable. At 6 weeks a kitten may still carry enough antibody to neutralise the vaccine virus, so the shot is neutralised too. The record looks complete, the owner is reassured, and the kitten is unprotected at 14 weeks. Three doses at 8, 12 and 16 weeks are the standard fix, because at least one of them lands after maternal antibody has fallen below the blocking level.

The dates, laid out

Age	Step	Maternal antibody left	Minimum weight	Record item
0-1 day	Colostrum; gut closes at 24 h	100%	90-120 g	Birth weight, colostrum taken
6 weeks	Health check, no vaccine	about 25%	550 g	Weight, temperature, eyes clear
8 weeks	Core dose 1	12-25%	700 g	Product, lot, site, date, weight
12 weeks	Core dose 2	under 12%	1100 g	Same five fields again
16 weeks	Core dose 3; series closes	under 5%	1600 g	Same five fields, next due date
17 weeks	7 days after last dose, litter may leave	own immunity	1700 g	Exit date, buyer details

Read the weight column as carefully as the vaccine column. A 16-week kitten under 1600 g is not a vaccination problem, it is a growth problem, and a kitten that has been losing weight should not be vaccinated on schedule. Weigh first, then decide. The 10 to 15 g per day rule that governs the first 2 weeks still tells you whether a 12-week kitten is on track, because a kitten that gained nothing between 8 and 12 weeks has something else going on.

Five fields that make a record usable

Most cattery disputes about vaccination come down to a card that cannot answer a simple question. Five fields fix that, and they take under 60 seconds to write:

1. The date given, plus the date the next dose is due.
2. Product name and lot number, copied exactly from the vial label.
3. Site and route: left or right shoulder, subcutaneous.
4. Age in weeks and weight in grams on the day of the dose.
5. The name of the person who gave it, and any reaction seen in the following 60 minutes.

A photo of the vial label pasted beside the entry costs 10 seconds and settles the lot number question permanently. Send the record with the kitten. A buyer who cannot show a date and a lot number will be turned away at a clinic that wants to know what was given at 8 and 12 weeks before it decides what to give at 20.

Why 16 weeks and not 12

Twelve weeks is where buyers push and where catteries give in. The argument for 16 is arithmetic. At 12 weeks a share of kittens still carry enough maternal antibody to block the dose, so a 12-week exit means some kittens leave with 1 effective dose instead of 2. The 16 week dose is timed to land after antibody has gone in nearly every kitten, and the 7 day wait covers the 5 to 7 days a vaccine needs to raise a response.

The rule worth writing into the contract is short: no kitten leaves before 16 weeks, and none leaves until 7 days after the last dose, whichever falls later. In practice that puts the exit date between 17 and 18 weeks. A kitten that leaves at 12 weeks meets a new home, a new box, a 2 hour car trip and 3 new people in 48 hours, then gets its next injection at a clinic that has never seen it. That is the sequence that produces a cough at 14 weeks and a booster history nobody can reconstruct.

Reactions worth writing down

Mild reactions are common and boring: sleepiness for 12 to 24 hours, a firm lump at the site that fades over 1 to 3 weeks, and a soft appetite for a day. The rare ones are the ones to watch. Facial swelling, vomiting or collapse inside 30 minutes is anaphylaxis and needs a clinic at once, which is why a kitten should stay in the room for 30 minutes after any injection. Do not vaccinate a kitten with a temperature under 37.5 C or over 39.5 C, or one that weighed under 700 g at the 8 week visit; a chilled kitten at 35 C responds poorly and the dose is wasted.

The cost side, for a litter of five

A litter of 5 on a 3 dose schedule means 15 doses and 2 or 3 clinic visits, spread over 8 weeks from first to last injection. Budget by litter, not by kitten, or you will under-count by 80% and quote a price you cannot hold. Current per-dose and per-visit figures are on the cost page; multiply by 3 doses and 5 kittens before you name a number to a buyer.

Fix the exit date at the same time. The rehoming timing guide sets the behavioural window at 12 to 14 weeks, while immunity points at 16 plus 7 days, and the two do not always agree. When they conflict, immunity wins and the kitten stays 2 to 4 more weeks.

What to do this week

• Weigh every kitten today and write the grams down; anything under 700 g at 8 weeks waits 7 more days.
• Book the 8, 12 and 16 week slots as one block so the 3 to 4 week interval cannot drift.
• Print a 5 field card per kitten and fill the lot number at the moment of injection, not at the end of the day.
• Set the earliest exit date at 17 weeks now and tell buyers at week 12, not at week 15.
• Check umbilicus, eyes and weight at every visit; the monitoring checklist uses the same 30 second per kitten routine.

Frequently asked