• Dr Izzy Smith

A look at Vaccine Hesitancy...

Updated: May 30


This is a collab post between @dr.amylouise (doctor in emergency medicine) + @doctorizzyksmith (doctor in endocrinology) 👏🏼😁


Everyday our immune system is exposed to various invaders in the form of viruses/bacteria/parasites but our body usually takes care of things without us even noticing! To put it very simply, our immune system is comprised of an innate + adaptive immune system. The innate immune system is like soldiers (macrophages + neutrophils) that attack anything that looks foreign. Whereas our adaptive immune system (B and T-lymphocytes + dendritic cells) is like the special forces that launch complex mediated attacks through the B cell’s creating antibodies against the infection or the T-cells directly attacking an infected cell.

If an infection becomes serious and the soldiers alone cannot handle it, the dendritic cells find the infection + show it to the T-cells which then activate the B-cells to send out antibodies. Antibodies are like missiles that fight infections and know what to attack by recognizing a unique protein on the pathogen called an antigen. This whole process can take many days to happen, which gives the infection a lot of time to do serious damage. Our bodies don’t like to fight wars like this often so it cleverly learnt how to “remember” invading pathogens through MEMORY B + T cells. This means the next time the body is exposed to the same infection; the memory cells can activate the same response but do so almost instantaneously and kill the infection before it has time to take off.

We can acquire antibodies through passive or active immunity.

PASSIVE IMMUNITY: a person receives antibodies from elsewhere e.g. mother-to-infant

ACTIVE IMMUNITY: a person’s immune system makes their own antibodies in response to either infection, vaccination or natural acquisition

2. What is vaccination, how does it work + what are the social implications?

It is estimated that vaccination programs prevent 2-3 million deaths per year. Vaccines work by creating the same immune response + memory cells our body would normally create when exposed to infection (as mentioned), but without having to actually get sick, suffer disability or die! There are different types of vaccines (DNA + RNA, live attenuated, inactivated, subunit and viral vector vaccines) which have similar principles + outcomes, but all achieve this slightly differently + have different pros + cons; @j_stokesparish has a nice summary of this.

Vaccines are rigorously evaluated for safety + efficacy and all undergo the same series of testing; Preclinical stage (animal/lab studies), clinical stages- is it safe? what’s the right dose? how effective is it? is it ready for larger studies? Is it ready for the general population? Regulatory approval, continuing trials- does it stay safe? Followed by manufacturing + quality control. All participants in vaccines trials are informed volunteers.

Herd immunity refers to when a large enough % of the population are immune through vaccination or natural immunity + that there is essentially no community transmission. This means people who are unable to be vaccinated due to medical reasons or newborn babies, are safe from contracting the illness. Unfortunately, due to vaccine hesitancy, conditions like measles + whooping cough are making a comeback, when previously, we had herd immunity against them. This is devastating as the vulnerable individuals who can’t be vaccinated rely on the majority of the population being socially responsible + getting vaccinated in order to keep them safe. The % of people who need immunity to create herd immunity will vary from different infections due to individual factors such as how contagious it is, but its usually between 70-90 %.

3. What is vaccine hesitancy + why does it occur?

It is characterized as the SPECTRUM between vaccination acceptance and refusal. Those who are vaccine hesitant (both within the general public + even health professionals!) are often on the fence between the two and the degree of hesitancy and refusal can be subtle or overt.

Vaccine hesitancy may result in

1. Delaying getting vaccines

2. Reluctant acceptance of vaccines

3. Vaccine refusal

4. Participation in the spreading of anti-vax rhetoric and propaganda

5. Increased outbreaks, morbidity, disability from illness or even death

The public health success of vaccination to date has resulted in new generations of people who are now unaware or unable to perceive the risks + magnitude of vaccine-preventable illnesses (which has lead to questioning + refusal). Despite a clear scientific consensus and burden of proof, the refusal of vaccines has lead to one of the top 10 threats to humanity, according to WHO in 2019.

It usually comes about as a result of:

1. Complacency (e.g. non-willingness to fact check information, ignorance of facts)

2. Convenience (e.g. easier not to get poked, pay money to be vaccinated + wait in lines at clinic etc)

3. Lack of confidence in the vaccines (Surprisingly people are more concerned if they are actually IMPORTANT or not rather than their safety. Lack of confidence can be due to lack of education or possible misinformation that person has been exposed to/ confirmation bias etc)

Hesitancy can potentially be a space for learning. It is important to note that it is normal for humans to question things + how we respond to those who are questioning vaccination can influence their choices and behavior going forward. Therefore, it is imperative to approach vaccination counseling in a compassionate way, loaded with all the facts and information. Where it becomes tricky is when the person being counseled has already become entrenched in science denial + has hard set beliefs that they are unable to question and this belief system is almost part of their identity (often from interacting in an echo-chamber with others who say and believe the same perspective). Not everyone will be receptive to vaccination counseling.

4. Addressing a few (general) vaccination concerns


Initial reactions are common and are different to side effects. It is normal to experience headache, fever, some swelling + redness at the site of injection and even fatigue after receiving a vaccine. Some children may even vomit within a few days after or develop a mild rash but it passes quickly. All of this is a sign that the vaccine is actually working + that the immune system has been recruited to FIGHT OFF the vaccine. The immune system then keeps a memory of that pathogen for future use (which also means vaccines don’t persist in the body after the immune system has fought them off + created memory cells) therefore, if there’s going to be any reactions it will be within the first few weeks to months at a maximum.

Side effects, on the other hand, are rare but can happen:

E.g. 1) Severe allergic reactions (e.g. anaphylaxis) about 1,3 in 1 mill vaccines*. This usually occurs in people with severe allergies who will already know if they have had a reaction to a vaccine or other meds in the past. In these circumstances, the patient should be referred to an immunologist who will advise on if it’s appropriate to miss the vaccine or be vaccinated in a controlled setting e.g. with pre-medications in a hospital environment. If in the very rare case the patient had no prior history of anaphylaxis, a standard general practice would still have the appropriate treatments + experience to manage a severe allergic reaction.

E.g. 2) Guillain-Barre Syndrome (GBS) + the flu vaccine. GNS is an auto-immune type condition that damages the nerves that control our muscles (causing ascending neuropathy + paralysis) and can occur in about 1 in 1 million flu vaccines. GBS is also caused by the flu itself and the incidence of it occurring from the vaccine is actually much less, so critical reasoning needs to be applied when considering this risk.


This fear is based on:

1. A small, sham study published in 1998 by Dr Andrew Wakefield stating that the MMR vaccine causes autism. Since then, there have been many studies on this involving over a MILLION children that shows that there’s no link between autism + vaccines (done by many scientists in many countries with different methods). This study has long since been retracted from the Lancet (it was found out he messed around with facts about patient medical histories, making the study incredibly flawed), he was struck from the register + he’s now become an avid anti-vaccine campaigner.

2. Concerns around mercury: Firstly, there are different types of mercury- thimerosal in vaccines is slightly different + less dangerous compared to the type of mercury found in fish or thermometers (methylmercury). There’s more mercury (+more of the more harmful type) in a tin of tuna than in a vaccine! And yes, mercury exposure in large DOSES does cause negative effects on the nervous system BUT the dose at which this occurs as a preservative in vaccines is so small. There have many different studies that were done showing NO link between thimerosal and autism + thimerosal has not been routinely included in childhood vaccinations for many years anyway.

3. Concerns around aluminum: Aluminum is often used as in vaccines to illicit stronger immune responses (but not in all of them, including the new COVID vaccine which doesn’t have aluminum adjuvant). Aluminum being neurotoxic or having the ability to cause autism has routinely been disproven in studies. Regardless, aluminum levels in vaccines fall way below the minimum risk toxicology levels (we consume much more of it naturally in our fruit and veg!) + is readily excreted (does not persist in the body) by the kidneys.


Nope! The risk of experiencing significant illness/disability or even fatality from getting a disease is much higher than if you got the vaccine for it e.g. especially with illnesses like polio, whooping cough, measles, haemophilus influenza etc … Essentially why would you risk your child getting sick, when you can get the same immunity benefits from a very safe vaccine?

For example, measles tends to be known (incorrectly) as a near-harmless childhood illness but the reality with a full exposure + experience of measles, is it can lead to 1-2 deaths per 1000 people or significant serious long-term illness like SSPE (subacute sclerosing pan-encephalitis) that causes long-term brain damage. Compare this with the very rare risk of getting an adverse reaction with the vaccine like encephalitis (very few reports of this in millions of people who took part in trials). In 2018 worldwide, there were several outbreaks of measles, especially in sub-Saharan Africa + approximately 140,000 children, mainly under 5 died. Due to increasing vaccine hesitancy we are also seeing measle numbers increase in areas with previous herd immunity such as the tiny island of Samoa (population 200,000) where there was 5,300 cases of measles and 83 deaths, due to vaccination rates dropping to around 83%.


We have loads of data showing each individual type of vaccine to be safe + together they do not have a major effect on the body. If we weren’t having vaccines, we would be being exposed to the real infections which would have a much greater effect on our immune system. Furthermore, we are exposed to many more immune “attacks” on a daily basis by exposures to bacteria and other bugs when we eat, breathe, shake hands etc, than we are from vaccines.

Claims that so many vaccines would overwhelm the immune system + increase rates of allergies or asthma are not true or evidence- based. The best study we have on this topic was a German observational study of 18,000 children (vaccinated + unvaccinated) which found no difference in allergic diseases or non-specific infections, or a smaller German study which followed 1,300 people from birth to 20, and found the vaccinated population actually had lower rates of asthma.

Essentially our immune systems are designed to multitask. Combined vaccines save time, money + discomfort, without evidence of adverse effects or increased rates of auto-immune or atopic type conditions.


Seizures have been reported for a few of the different vaccines but it is rare e.g. 1 in 14000 for the DTAP vaccine etc.

These are usually as a result of what we call febrile seizures which means the seizure is triggered by a rise in temperature (the normal immune response after receiving the vaccine) rather than from the vaccine ingredients themselves. Children who are prone to febrile seizures usually get them with anything that would’ve caused a rise in temperature such as a urinary tract infection and occur in 1/30 children at some point in their life (i.e. not limited to a vaccine response only).

Obviously, this can be frightening for parents, but it’s important to highlight that;

1) They rarely occur from vaccines

2) they are benign + usually resolve quickly

3) they do not cause brain damage or increase the risk of long-term epilepsy

4) Children would be at greater risk of having a febrile seizure if they caught the illness itself

5. Why science/ medicine will never compare previous vaccines to a placebo

The anti-vaccine movement commonly demand for a randomised controlled of vaccinated vs unvaccinated children, to supposedly prove that vaccines aren’t required as unvaccinated children would have similar health outcomes to vaccinated children.

There are many issues with this argument and why such a study would not be ethically possible, or prove that vaccines are or aren’t needed (with the exception of the new covid vaccine which is discussed below).

In a clinical trial it would be completely unethical to not give one group vaccines when we already have so much evidence for their safety and efficacy… E.g. It would be like wanting to do a study on the safety of seatbelts to test if they save lives or do a study on if smoking really increases the risk of lung cancer. Like a RCT on vaccination, both of these examples would be absolutely ludicrous + unethical based on current evidence.

In a similar way, this is also why some clinical trials are stopped early if it’s immediately evident that the intervention arm is more or less efficacious or if its in safe- it would be unethical to continue.

Furthermore, even if such a trial did go ahead, in any area which had herd immunity, the results would not indicate efficacy of vaccines as the unvaccinated group, would still have safety from these infectious diseases on the basis of herd immunity.

The only time a RCT would be ethical or clinically useful for a vaccine, would be if the efficacy of the vaccine was unknown and there was not herd immunity for the given disease already. This is exactly the situation with the Covid and why there have been several large RCTs for the Covid vaccine (which thankfully have demonstrated their efficacy with minimal side effects).

6. The anti-vax movement is a billion dollar industry

Firstly, doctors or any other healthcare professionals are not paid money to promote vaccination. We promote it because it saves millions of lives every year + we promote it for the social and public health implications for our patients. As an example, we (Dr Amy and Dr Izzy) work in specialties that rarely administer vaccines (emergency and endocrinology) but are so concerned about the impact of vaccine hesitancy that we have spent hours and hours creating this recourse.

Secondly, it is not always easy for vaccine companies to make profits as researching and making new vaccines is a VERY expensive process. But yes, if vaccine companies do succeed, in the end they will money which is the reality of any business in a capitalist society. Everything is done to make money, even when it has good intentions behind it, like prevention of disease spread, farming of affordable food, or investing in renewable energies. With this in mind, it’s important to note that every time a vaccine refusal video/ post is shared or a homeopathic “vaccine” or natural immune “booster” is sold, people also make money. A lot of it!

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