Fact vs Myth: Vaccines


Vaccines have recently become a controversial topic amongst dog owners, and there is a lot of misinformation out there. We’ve decided to separate out the myths from the facts so you can make the right choices for your pet.

What are vaccinations?

Vaccines are amazing things. Inside that little glass bottle at the vets is a whole lot of science that has been developed over hundreds of years. In essence, a vaccination involves injecting a small amount of disease with the intention of teaching the immune system how to recognise and fight the disease in a safe and controlled manner.

Vaccinations were first invented by Edward Jenner in the 1790s. He noticed that the milkmaids who got cowpox didn’t die of smallpox, one of the deadliest diseases of the time. So he took the pus from a cowpox boil and spread it into a cut on a little boy’s arm. A little while later, he spread smallpox into a new cut, the child survived the smallpox and vaccination was born. Vaccination allowed smallpox to eventually be eradicated worldwide.

Nowadays, the process of making a vaccine is far more carefully controlled

We also understand a little more about why it works. When the body meets a disease, it first has to search for the white blood cell that can fight it. In adult humans and animals, there are so many white blood cells in the body that at least 30 of them are available to fight any disease you could ever come across. The problem is that 30 is not enough- once the body has found the white blood cell with the right ‘key’, it has to clone them until it has enough to fight the illness. This takes about a week, during which time the disease can cause a lot of damage. 

So, scientists take the virus or bacteria. They either kill it or modify it so it can’t cause disease, and then inject it. This gives the body a chance to find the right key and replicate then practice fighting off the invader. The cool part is that, once the disease has been destroyed, some of these white blood cells become memory cells. This time there are far more than 30. This means next time the disease is encountered they can put up a fight much more quickly.

So now you understand the science behind vaccinations, let’s look at some common myths about vaccines and vaccination.

Myth: “Dogs only need their puppy vaccines”

Fact: Unfortunately, those cells that ‘remember’ the key to the disease don’t live forever. And not every vaccination results in a successful immune response. How long the cells live depends on the type of immune cell that does the remembering, as well as lots of other processes in the body. It also depends on how often the disease has been encountered. And if the initial vaccination didn’t cause a suitable immune response, there won’t be any memory cells to protect the dog next time.

Vaccinations need to be repeated at various intervals. These are determined by measuring the number of memory cells left at various periods after injection in a group of dogs. Remember though, the vaccination leaflet has to give the minimum repetition time – so although one dog might be ok for seven years, the next may not have sufficient cells left after three, so the vaccine schedule will recommend repeat 3-yearly to make sure everybody is protected.

Myth: “Humans don’t need boosters, so dogs don’t either.”

Fact: This isn’t actually true – depending on the vaccine, many diseases need re-vaccination in adults. It all depends on the length of time the memory cells live for in the average population. As well as how common the disease is, how much the disease changes year to year, how many people have received the vaccination and therefore can’t spread the disease if your vaccination wanes (what we call ‘herd immunity’) and how deadly the disease is to adults.

Myth: “Vaccination causes autism”

Fact: This bizarre myth has been taken from a paper written by a doctor in the late 90s. It was later found that he’d misrepresented the results. He was paid over £400,000 to find a link. He was struck off for doing so and is no longer allowed to practice. Unfortunately, despite more than 12 further studies finding no link, the myth is still perpetuated by many. 

Myth: “Some vaccinations are dangerous and can kill… you should never give your dog L4”

Fact: Whilst a lot of people currently believe that the Nobivac L4 vaccination against leptospirosis is more dangerous than the L2 vaccination. There is no scientific evidence that this is the case. Vets have an obligation to report any suspected side effects (major or minor) or reactions to the Veterinary Medicines Directorate (VMD). They then investigate these and determine whether they are truly side effects or just coincidences. In one report from the VMD, the total number of investigations for L4 were less than 7 for every 10,000 doses. Most of these were discounted as they weren’t found to be related to the vaccination. Those that remaining were often very minor. It was recommended that the datasheet was adjusted to say injection can be painful if the vaccination is administered cold. So pain at injection was the most common reported side effect.

Whilst no medical intervention, vaccination included, is considered to be completely safe, in every case the vet and pet owner have to weigh up the risks against the benefits. Since leptospirosis is a disease that kills pets, and is also deadly to people that might catch it from their pets, for the vast majority of dogs the benefits of vaccination clearly outweigh the tiny chance of a risk.

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