Vaccinating dairy animals poses challenges that are not seen in the beef herd.
•    Unlike the beef herd, cows calve all year round, so the ages of young animals requiring initial vaccination are different. The way around this is to vaccinate young stock in groups eg a vaccine supposed to be given at 6 months can be given to a group aged 4 – 8 months.
•    Some vaccines have a withdrawal period for milk and meat. These should be given to cows in the dry period PROVIDED THEY ARE SAFE FOR PREGNANT ANIMALS. If not – the loss will have to be carried and the milk discarded for the withdrawal period.
•    Some vaccines cannot be given to pregnant animals. These should be administered to heifers before breeding and to cows in early lactation before breeding.
It is obvious that record keeping has to be exceptional to keep track of which animals have been vaccinated when against what ! If not – animals may be vaccinated twice, may be vaccinated too old (Brucellosis) or may not receive a vaccination at all.
It must also be remembered that vaccination does not always give full protection against disease. Management, scouting for disease and nutrition are the best tools for keeping the herd healthy and disease-free.
The following are some of the vaccinations that should be administered to the dairy herd. Situations vary from farm to farm and your veterinarian is the best person to advise what vaccines are essential for your particular conditions.
Brucellosis (Contagious Abortion) BRUCELLA S19
As Brucellosis is a zoonosis of man, the vaccination against CA is controlled by law. All heifers must be vaccinated between the ages of 3 – 9 months, ideally by 6 months. Vaccination before 3 months will interfere with maternal immunity and vaccination after 9 months may show a false positive for the disease when testing in later life. A new vaccine is on the market which does not show a rise in antibodies. Brucellosis vaccine is only given once.
Vaccinate all calves initially at 6 months and boost 1 month later. Vaccinate at 1 year and then annually.
Vibrio is a veneral disease of cattle cusing abortion and infertility and can have devastating effects on a dairy herd. Vaccinate all breeding heifers and young bulls 2 months before breeding, boosting one month later. Annually vaccinate all empty cows one month before breeding. 
Bulls may remain carriers despite vaccination and should be tested if you suspect they may have the disease.
Leptospirosis VIBRIO LEPTOFERM 5 
A venereal disease of cattle that  is also a zoonosis of man. Cattle should be vaccinated at the same time as for vibriosis. Often the vaccine is a polyvalent, containing both vaccines.
Anthrax is endemic in Zimbabwe and is a fatal disease of animals and man. Some veterinarians advise vaccinating all stock regardless of whether the farm is in an Anthrax area. Vaccinate the calf at 3 – 6 months and then annually at least until the animal is 3 years old.
More commonly found in beef herds eating old bones but should be given if chicken litter is fed. Vaccinate at 3 – 6 months, boosting 1 month later and again at 18 months.
Bovine Viral Diarrhoea
A disease mainly of calves, cows are given the vaccine to impart prenatal immunity to their calves. There are 2 forms of the vaccine. A killed vaccine is suitable for use in pregnant cows, but does not give as good protection. The live vaccine should be given to calves at 6 weeks, 6 months and 2 months before breeding.
Rabies DEFENSOR 3 10 D
Fatal to man and animals. If in a rabies area, all animals should be vaccinated. Consult your veterinarian.
Calves whose mothers have been vaccinated should be vaccinated at 6 months so as not to interfere with pre-immunity. Claves whose mothers were not vaccinated – vaccinate at 3 months. Repeat annually for at least 3 years.
Rift Valley Fever
Vaccinate the whole herd prior to the rainy season
Other vaccines that may be required are Calf Paratyphoid, Tetanus, Pasteurella ( at 4 moths, 5 mths, 1 yr, annually) Mallignant Oedema, IBR (Infectious bovine rhinotracheitis) , SCOURGUARD 4
•    Too much dependence on vaccination to solve  management problems. Vaccines generally only   work if other management methods to reduce  disease are implemented.
•    Failure to give a proper primary course of killed vaccines 2 - 4 weeks apart, as specified by the manufacturer.
•    In the case of  leptospirosis: not giving the booster doses often enough.
•    Not establishing a correct diagnosis, and consequently using the wrong vaccine.
•    Strain differences in the disease causing agents, e.g.,    BVD, pinkeye, Staph. aureus mastitis.
•    Incorrect use or dosage of the vaccine.
•    Improper storage of live vaccines.
P Jackson