Post vaccine symptoms in children (also post covid vaccine): what they are and what to do if they occur

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Philippe Gloaguen
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Vaccines are considered today among the most controlled and safest pharmaceutical products.

Precisely because they must be administered to healthy people, especially children, they must respect particular safety standards, even more rigid than those provided for other drugs. In addition, companies that need to develop vaccines tend to have a low tolerance for any adverse reactions.

Why then are vaccines so feared by many people including some parents? Often, the main reason is that potential adverse reactions are feared and one therefore thinks that it is less risky to contract the disease than to vaccinate one's children. But this, as we will see below, is absolutely not true.

Of course, some symptoms may occur after vaccination, but they should not be a cause for concern, when they do occur it is almost always a matter of mild symptoms and absolutely transient. Let's see them together thanks also to the help of dr. Enrico no, full professor of Pediatrics and Director of Neonatology at the Città della Salute e della Scienza University of Turin.

In this article

  • why some post vaccine symptoms occur
  • non-vaccine-induced events
  • possible post vaccine symptoms
  • how to relieve post vaccine symptoms
  • severe vaccine reactions
  • the risk of the vaccine and that of the disease
  • are vaccines safe?
  • What to do if a vaccine adverse reaction is suspected?
  • Vaccines and Autism: An Unfounded Belief

Why do some post vaccine symptoms occur

First, let's try to explain how a vaccine works in a simple and effective way. The vaccine simulates a first "encounter" with the infectious agent which causes disease and so goes to stimulate our immune system. She in a nutshell she instructs him, teaching him to react to antigens of the pathogen and inducing an immunization against the disease.

As reported by the Istituto Superiore di Sanità, precisely because following the vaccine there is one immune response, it is normal that some mild and transient symptoms may occur.

"Many times the so-called side effects of a vaccine are actually the sign of one response of the organism. Parents don't have to worry if the baby gets some fever, it is a "positive" thing because it means that the organism has responded to the vaccine "explains Prof. no.

Read also: Fever in children: the answers to the 8 most common doubts of mothers

Events not caused by the vaccine

Before seeing what are the symptoms that can occur following the vaccine, prof. no makes a necessary clarification "it must be premised that very often most of the events that are believed to be related to the administration of the vaccine, in reality have little to do with the vaccine itself, it is random effects". Often, in fact, we are faced with totally random effects that occur in a period of time close to the administration of the vaccine and this leads many parents to think that the cause was the vaccine, but it may not be.

We can speak of an adverse reaction to the vaccine when it is certain that the vaccine has caused a certain unwanted manifestation. Parents can contact the pediatrician or vaccinator if they arise suspicious symptoms after vaccination. "The adverse events to vaccination will be evaluated by expert personnel who can establish or not, through scientific criteria, if there is a cause-and-effect link with vaccination "- he explains no, who then adds" in Del Paese it is the Del Paesena del Drug Agency (AIFA) that deals with reporting system adverse events. We doctors compile some forms in case of unwanted reactions that are sent to AIFA, which will take care of evaluating if they really are events to be associated with the vaccination or not ".

So let's see now what are the post vaccine symptoms that can arise in children.

Possible post vaccine symptoms

Some symptoms or side effects may appear after a vaccination, just as they can when we take a drug. Usually, however, there is a tendency to give little weight to the possibilities adverse effects of common drugs such as paracetamol or antibiotics, while when it comes to vaccines, possible post-administration reactions are not well tolerated. It may be more difficult for parents to accept the risks of the vaccine because we are in fact "injecting something" into a healthy child and this can raise doubts and fears. The scientific evidence actually shows that even if the vaccine causes adverse reactions, it usually is mild effects e transient. We distinguish the reactions in:

  • reactions local which include swelling, pain and redness where the vaccine is injected;
  • reactions generalized such as general malaise, lack of appetite, fever, crying, vomiting, diarrhea, swollen lymph nodes, spots on the baby's skin.

"This type of reactions - explains Prof. no - can occur at a distance of 24 / 48 hours from the vaccine, but also after 7 or 10 days if it's about the measles vaccine. "

Not all children necessarily experience a reaction after the vaccine, but in generally the most common is fever. What should be done then if the child has some mild reactions to the vaccine?

Covid vaccine in children: what are the possible adverse effects?

After the Covid vaccine, the child may experience some mild side effects such as:

  • pain, redness and swelling in the arm where the injection was given;
  • tiredness, headache, body aches, chills, fever and nausea which usually resolve within 1-2 days.


And what about the famous cases of myocarditis instead? The National Institute of Health replies to this: "In young subjects (adolescents and young adults) an increased risk of myocarditis and pericarditis has been reported, which however remains extremely low, around 50 cases per million after two doses. In most cases, moreover, such manifestations had a absolutely benign course. In general in the younger children there is a lower risk of developing these diseases, and no cases have been reported during clinical trials. The safety information available today concerns not only the 3000 children who received the vaccine as part of the clinical trial, but also includes the first data collected in the over 3 million children of 5-11 years already vaccinated in the United States ".

Judging by what we have seen in teenagers, however, the post-vaccine myocarditis they are very rare disorders that resolve themselves in a short time. Not to mention that the cases of myocarditis that occur after Covid-19 are many more and much more serious.

How to relieve post vaccine symptoms

Generally, all the mild manifestations that can occur following the vaccine resolve on their own even without the help of drugs. However, if we prefer to relieve an ailment such as fever or try to calm the child who is a little restless due to the pain, we can administer ibuprofen or acetaminophen as recommended also from the Guide to contraindications to vaccinations drawn up by the main scientific societies dealing with child health. If on the other hand the child complains because the area where the vaccine was administered appears swollen and red, a wet cloth with fresh water or an ice pack can be applied to relieve pain.

As we have seen, not all children experience unwanted reactions after the vaccine, which is why pediatricians inadvisable to administer an antipyretic before vaccination.

Read also: Children and drugs: when to use ibuprofen and paracetamol

Severe reactions to the vaccine

What scares some parents the most when it comes to vaccines are the possible adverse reactions, particularly severe ones, but it doesn't have to be. Serious adverse events are so rare and completely unpredictable that only when millions of doses of a given vaccine have been administered can these unwanted reactions be detected and recorded.

When we talk about serious side effects, we are talking about cases defined as rare or very rare and that means that they occur on average in one case in every million doses of the vaccine administered. That is why parents should fear the effects of the disease much more than those of the vaccine that prevents it.

Among the reactions considered serious that occur following vaccination, but which generally resolve without consequences for the child in the long run, we find:

  • febrile seizures;
  • thrombocytopenia - reduction in the number of platelets;
  • hypotonia - decreased muscle tone;
  • hyporesponsiveness: reduced response to stimuli;
  • uncontrollable crying;

With regard to febrile seizures the professor. no he is keen to point out that the vaccine is not to blame. "If the child has febrile seizures it does not mean that it was the vaccine that caused them, but that we are dealing with a child already predisposed to seizures in the presence of febrile states".

They can also rarely occur severe allergic reactions occurring within a limited time after vaccination. "The latter could be avoided thanks to an accurate pre-vaccination history which allows health personnel, thanks to some specific questions, to evaluate the suitability for vaccination. "A good medical history, in fact, has proved to be the most effective method for assessing theadmission to the vaccine.

Finally, in order to ensure greater safety, precisely because of the possible unwanted reactions, the parents of the children are asked to wait about half an hour in the clinic where the child was vaccinated. So if there are particular post vaccine symptoms, health personnel can intervene immediately.

So, if possible serious reactions are truly a rare occurrence, why do some parents come to think that the vaccine is more dangerous than the disease it is intended to prevent? In this regard, it can be really useful to compare the available scientific evidence regarding the risk that a disease carries with the risk associated with vaccination for the same disease.

The risk of the vaccine and the risk of the disease

When it comes to a "hot" topic like vaccines, any doubt or fear of parents must be listened to, understood and never laughed at. "Parents only want the good of their children, but sometimes it can happen that they run into it incorrect information or incomplete regarding vaccinations and therefore misconceptions are made, especially today in which dr. Google is saturated with uncontrolled information "explains Dr. no.

This is why it is often easy for some mothers and fathers underestimate the possible harm of a disease and instead overestimating the risk of administering a vaccine.

But let's see in detail the risk-benefit ratio of vaccines and some of the diseases that can be prevented with vaccination.

Let's take the MMR (measles-mumps-rubella) vaccine as a first example, what are the adverse reactions to the vaccine? "Between mild reactions, as with other vaccines, there is a fever which may be accompanied by a rash which can occur one week to ten days after the vaccine. Between the most serious risks deriving from the vaccine, on the other hand, we find the risk of encephalitis or a severe allergic reaction, but we must ask these events what probability they are likely to occur. We talk about one case in every million vaccines administered".

Let's now try to compare these risks with the risk from diseases such as measles, mumps and rubella.

"The scientific evidence - he explains no - shows us that when a child contracts the measles the effects can be far more serious than those that the vaccine brings with it. "In fact, the data speak for themselves. measles cause

  • pneumonia: 1 case out of 20;
  • encephalitis: 1 case out of 2000;
  • death: 1 case in 3000

With regard to the mumps, instead, we even have 1 case of encephalitis in every 300. And rubella, although less severe, if contracted in early pregnancy causes congenital rubella in 1 in 4 cases.

"You can see from these numbers that the cost-benefit ratio is all to the advantage of the vaccine."

For the sake of completeness, we now also analyze the risks of the DTP vaccine (diphtheria, tetanus, pertussis) with the risks associated with the diseases from which the vaccine protects.

"The vaccine against diphtheria, tetanus and pertussis causes in 1 case its 100 un inconsolable crying that passes and can be soothed with paracetamol; in 1 case its 1750 of the convulsive form without any subsequent damage; in 1 in 1 million cases of vaccine doses, aacute encephalopathy". What do we face instead if we do not carry out this vaccine?

La diphtheria cause:

  • death: 1 case out of 20
  • cardiac complications: 1/2 cases out of 20
  • neurological complications: 2 cases out of 10

Il tetanus causes death in 1/2 out of 10 cases. And, finally, the whooping cough it can cause pneumonia in about 2 in 10 cases, and be fatal in one in 100 cases.

Comparing the numbers relating to the risks of a disease, with the risks deriving from the vaccine, it should be clear that vaccinating children is one of the wisest choices that parents can make towards their children. But if you still have any doubts, do not worry, let's try to investigate even better why vaccines are really safe.

Read also: Tetanus: the disease, the treatments, the vaccine

Are the vaccines safe?

It depends on what we mean by "safe"! "If we mean as safe a vaccine it doesn't have no side effects, then clearly no vaccine is safe, just like no drug, no medical practice and no human activity "says Prof. no." A vaccine is safe when, despite having possible and rare side effects these are sharply less than the benefits that derive from the administration of the vaccine. "The possible side effects should always be compared with the risks of the disease which, as we have seen above, are much higher.

But how can we be sure that vaccines are safe? Because before approval a vaccine must be tried out to evaluate its tolerability, safety and the ability to induce an effective immune response, whether administered alone or in combination with other vaccines. After authorization, the vaccine manufacturing processes are carefully monitored and analyzed to ensure safe vaccines for all of us. The production must in fact respect rigidissimi standard indicated by the World Health Organization and the European Medicines Agency. Finally, even after the marketing there is a constant detection of possible adverse effects related to the administration of the vaccine, thanks to the collection of reports made by health professionals and citizens.

What to do if a vaccine adverse reaction is suspected?

When a parent takes their child for the vaccine, health professionals inform them of the possibility of the child experiencing symptoms or adverse reactions and then advise them on what to do if any of these symptoms occur.

In principle, it is a good idea contact the pediatrician or the pediatrician of the hospital reference when the child after vaccination:

  • has a body temperature above 40 ° (axillary);
  • he is very faint and pale;
  • experience tremors, twitches, or sudden jerks;
  • cries continuously for more than three hours or cries unusually.

Even if therestlessness or redness post vaccine does not disappear after 24 hours it is advisable to contact the pediatrician or the vaccination service.

When there is a suspected adverse reaction to vaccines health professionals, vaccination centers and citizens can report it through the website The information will then be sent to the national database of the Del Paesena del Farmaco Agency (which deals with pharmacovigilance). AIFA in turn will share the data with the European Medicines Agency and with the World Health Organization. Thanks to the reports it is possible to intervene in a timely manner and in case of suspicious reactions withdraw the vaccine immediately from the market. Where it happened it was later found that the alarm was unwarranted, but this makes us understand that we can be confident about the safety of commercial vaccines.

Finally, to try to clarify yet another possible doubt about the safety of vaccines, let's answer a very last question: what is the relationship between vaccines and autism?

Vaccines and Autism: An Unfounded Belief

The history of the unfounded correlation between autism and vaccines dates back to 1998 when a prestigious scientific journal (Lancet) published an article by Dr. Andrew Wakefield in which the doctor argued that there was a link between measles-mumps-rubella vaccination and autism.

The hypothesis, however, turned out to be devoid of scientific evidence. After many years, and as many scientific studies, Lancet has decided to officially withdraw the publication. In fact, not only was there no correlation between the two, but Wakefield was also discovered falsified data of his own research as he was hired by a lawyer who dealt with trials for vaccine damage, a nice conflict of interest in short.

The reality is that no matter how much you want to look for a culprit at all costs, the vaccine does not cause autism, which does has a genetic basis e it could be diagnosed even before vaccination with adequate techniques.

Unfortunately, even today these theories are used by the anti-vaccine movements to instill unmotivated doubts and fears in parents, so much so that over the years some, albeit small, have been recorded. measles outbreaks due to a decline in MMR vaccination.

Updated on 24.12.2022

  • vaccinations for children
  • adverse reactions to vaccines
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