All about vaccination

Last updated on 17.02.2022

We can do it together!

Vaccination is the most effective means to combat the COVID-19 virus, which has caused a pandemic and paralyzed countries, families, society, and individuals around the world. Excellent scientists as well as historical facts clearly show that usage of safe and effective vaccine is the best way to defeat any virus. COVID-19 vaccination offers not only protection for an individual who is vaccinated, but also collective protection of the community and whole society. When a person is vaccinated, transition of the infectious disease to other people is less likely. It means, that vaccination helps protect those who themselves cannot be vaccinated.

Vaccination will protect people from the disease and prevent the spread of the disease in the population and thus minimize number of deaths, minimize the overload of acute and intensive cases in health facilities, protect health workers, risk groups, and enable gradual return to life without restrictions.

In case of COVID-19 it is necessary to vaccinate 60 - 70 % of population to achieve national collective immunity.

Vaccination helps keep more people healthy and reduce social and psychological impact of the disease on people as well as burden on hospitals and healthcare systems. Thus, resources can be used to fight other diseases such as cancer or Alzheimer's disease.

While individual immunity to the virus protects the individual, collective immunity prevents further spread of possible infection and works as prevention against epidemics or pandemics. Individual immunity can be gained by overcoming a specific disease or by vaccination.

Collective immunity depends on millions of responsible decisions taken by individuals. Depending on the number of vaccinees, the spread of the disease slows down and long-term vaccination of the majority of the population may result in lasting collective immunity.

For the following reasons, Covid-19 vaccines available in Slovakia are safe:

  • All vaccines underwent multi-phase clinical trials based on large number of volunteers. They have been later reviewed and approved by European Medicines Agency (as well as many other medicine agencies from other countries).

Learn more about how clinical trials work in the video:

  • The results of clinical trials are being confirmed in practice by vaccinating millions of people around the world. Side effects other than those on the package leaflet are extremely rare and the benefits of vaccination outweigh the risks.
  • All side effects from the package leaflet are short-term. Long-term side effects of the vaccine, which would only become apparent over a long period of time, are generally rare. None of the 82 vaccines registered in the Slovak Republic have been deregistered due to side-effects occurring long time after vaccination.

Comparison of long-term vaccine side effects vs. long-term consequences of COVID-19

(read the package leaflet for Comirnaty vaccine issued by Pfizer/BioNTech)

(please, read the vaccine package leaflet issued by Moderna)

(please, read the vaccine package leaflet for  COVID-19 Vaccine AstraZeneca)

All the vaccines approved by the European Medicines Agency must undergo clinical trials and prove to be safe, they must be sufficiently effective to have a satisfactory benefit/cost ratio.


The following information applies to Comirnaty vaccine by Pfizer/BioNTech


Adequate protection against COVID-19 begins 7 days after administration of the 2nd dose. According to the current state of knowledge, about 95 out of 100 vaccinated people are protected against the disease.

A large clinical trial proved 95 % effectiveness of Comirnaty vaccine against COVID-19 in people aged 16 years and older. A total of approximately 44,000 people participated in the study.

Half of them received the vaccine and the other half received placebo. Individuals did not know which group they were included in.

Its effectiveness has been evaluated in approximately 36,000 people aged more than 16 (including people over 75 years of age) who did not have symptoms of previous infection.


The study showed 95 % reduction in the number of symptomatic cases of COVID-19 in people who received the vaccine:





Number of people in the group



Number of people with symptoms after vaccination






18 198









18 325






Efficiency of 95 % was also confirmed in people with a potentially severe course of COVID-19, such as asthmatics, people with chronic lung diseases, diabetes, or high blood pressure.

It is currently unknown how long this protection will last. Seeing that protection does not start immediately after vaccination and does not develop in all vaccinated persons, it is necessary to protect yourself and others and follow the rules despite being vaccinated (please, keep your distance, maintain hygiene, wear a face mask, air your premises regularly).


The following information applies to COVID-19 Moderna vaccine produced by Moderna


COVID-19 vaccine Moderna

Following recommendations by the European Medicines Agency, the European Commission granted a conditional marketing authorization for COVID-19 - Moderna vaccine against COVID-19 in early January (January 6th, 2021).


Is COVID-19 vaccine Moderna safe?

The COVID-19 vaccine Moderna offers a high level of protection against COVID-19 in the current pandemic situation. Extensive clinical trials have proved the vaccine to be 94.1 % effective. Severity of side effects caused by COVID-19 Moderna ranged usually from mild to moderate and improved within few days after vaccination.

The European Medicines Agency has therefore decided that the benefit of COVID-19 Vaccine outweighs the risks associated with its use and recommended it for marketing authorization in the EU.

Data concerning the use of COVID-19 vaccine Moderna are continuously being monitored, as it is with other drugs and vaccines. Reports of suspected side effects caused by a vaccine are being carefully evaluated and all necessary measures to protect patients have been taken.

As COVID-19 vaccine Moderna has received conditional marketing authorization, the producer of the vaccine will continuously provide results of clinical trials for the next two years. This and other studies will provide even more precise information on the duration of protection after vaccination, on the prevention of severe forms of COVID-19, or how to protect people with compromised immunity, children, or pregnant women.

In addition, independent studies of COVID-19 vaccines coordinated by EU authorities will provide more information on the long-term safety and benefits of the vaccine for general population.


Is COVID-19 Moderna vaccine effective?

Extensive clinical trials including almost 30,000 volunteers have proved the effectiveness of COVID-19 Moderna in adults aged 18 and older.

The study proved a 94.1 % reduction in the number of symptomatic cases of COVID-19 in people who received the vaccine (11 out of 14,134 vaccinated people suffered symptomatic COVID-19) in comparison with people who were administered sham injections (185 out of 14,073 suffered symptomatic COVID-19).

The study also proved 90.9 % effectiveness in participants expected to suffer severe COVID-19 including patients with chronic lung diseases, heart diseases, obesity, liver diseases, diabetes, or HIV infection.

How many times do I need to be vaccinated?

COVID-19 vaccine Moderna is administered in two injections into an arm in the interval of 28 days.

Should it be impossible for you to attend the 2nd dose of the COVID-19 vaccine Moderna, please, make another appointment with your doctor as soon as possible. Should you not be administered any vaccine, you may not be completely protected against COVID-19.

Do I need to be vaccinated with COVID-19 vaccine Moderna every year?

It is currently unknown how long the protection by COVID-19 vaccine Moderna lasts. People vaccinated in a clinical trial will be further examined for 2 years to obtain more information on the length of protection.

In which cases should I not be vaccinated with COVID-19 Moderna?

  • Children

COVID-19 Moderna is not recommended for children and adolescents under 18. The European Medicines Agency and the vaccine producer plan to test the vaccine in children in the future.

  • Pregnant and breastfeeding women

Animal studies do not indicate any harmful effects during pregnancy. However, data on the use of COVID-19 Moderna during pregnancy are limited. Although there are no studies related to breast-feeding and vaccination, no risks are expected. If you are pregnant or breastfeed, think you may be pregnant or planning to get pregnant, please, consult the administration of the vaccine with your doctor, pharmacist or nurse.

  • Other medicines and COVID-19 vaccine Moderna

If you take or have recently taken or might take any medicines in future, please, inform your doctor or pharmacist of the fact. COVID-19 vaccine Moderna may affect the way other medicines work and other medicines may affect the way COVID-19 vaccine Moderna works.

  • People with compromised immune response

Only limited data concerning people with compromised immune responses are currently available. Although people with a compromised immune system may not respond well to the vaccine, there are no particular safety concerns. People with weakened immunity can also be vaccinated as they are at greater risk of developing COVID-19.

  • Allergies

People who know they are allergic to some kind of drug or any component contained in Moderna, should not be administered this vaccine.

Allergic reactions (hypersensitivity) have been observed in people who received the vaccine. There have been very few cases of anaphylaxis (a severe allergic reaction). Therefore, as with all vaccines, COVID-19 vaccine Moderna should be administered under strict medical supervision and appropriate medical treatment should be available in case of allergic reactions. People with severe allergic reaction after the administration of the first dose of COVID-19 vaccine Moderna should not be administered the second dose.

What side effects may occur with COVID-19 vaccine Moderna?

Like all medicines, this vaccine can also cause side effects, although not everybody will experience them. Severity of COVID-19 Moderna side effects ranged usually from mild to moderate and improved within few days after vaccination.

Please, seek immediate medical assistance if any of the following symptoms of allergic reaction occurs faintness or dizziness, changes in heart rhythm, shortness of breath, wheezing, swelling of lips, face or throat, hives or rash, nausea or vomiting, stomach pain.

Should you experience any side effects, please talk to your doctor or nurse. These may include the following:

Very frequent (may affect more than 1 in 10 people): swelling in the armpits, headache, nausea, vomiting, muscle and joint pain and stiffness, pain or swelling at the injection site, feeling very tired, chills, fever.

Frequent (may affect less than 1 in 10 people): rash, redness or hives at the injection site.

Less frequent (may affect less than 1 in 100 people): itching at the injection site.

Rare (may affect less than 1 in 1,000 people) temporary unilateral facial paralysis (Bell's palsy), swelling of the face (swelling may occur in patients who have received cosmetic injections into the face).

Unknown frequency - severe allergic reactions (anaphylaxis), hypersensitivity.

Allergic reactions have occurred in people who have been administered the vaccine, including a very small number of cases of severe allergic reactions (anaphylaxis). Like all vaccines, COVID-19 Moderna should be administered under close medical supervision and with appropriate treatment.

(please, read the vaccine package leaflet issued by Moderna)

How COVID-19 vaccine Moderna works

The COVID-19 vaccine MODERNA works on the principle of mRNA, which is, in simple words, the carrier of a genetic instruction. Even simpler, it is a guide by which our body can create one part of the virus. Specifically, it creates the characteristic protrusion of the coronavirus that you see in each of its graphic depictions or illustrations. This protrusion is called the spike protein and is located on the coronavirus envelope, which is why the virus is able to enter human cells.

Thanks to this guide found in the mRNA vaccine, our body is able to produce this part of the virus. The immune system then recognizes it as a foreign element in our body and triggers a defence reaction - begins to form antibodies and T-cells. Thanks to this "training" our body receives, we shall become resistant to real corona virus.

Vaccines based on mRNA principle represent a new type of vaccines, which is perhaps one of the reasons why some people are concerned about this technology. However, mRNA vaccines are not entirely new, in fact they have been studied for several years in relation to other diseases and have been used repeatedly in clinical trials.

There are many myths and misinformation on the issue. Though, development of vaccines usually takes many years. Therefore, it is perfectly natural to ask how this process could be sped up so significantly in case of an anti-COVID vaccine.



- The development of a vaccine for COVID-19 has become an absolute priority in scientific and pharmaceutical circles this year. An enormous amount of energy and financial resources have been poured into it at the cost of postponing other projects. Vaccine producers could therefore be able to maximize the number of experts and scientists who have worked on vaccine development.

- Many of the processes related to vaccine development and testing have been optimized and bureaucratized, but never at the expense of its safety. Clinical trials as such comply with standards. Simplified and accelerated are processes happening around them.


- The individual phases of the preclinical and clinical trials follow one after the other in normal circumstances. In this case, they ran in parallel - before the first round was completed, the second round had started. Thus, volunteers may be potentially at greater risk at each stage of the clinical trial, but the final product must go through all stages just like any other vaccine. The final vaccine will be just as safe.


- Due to the pandemic and the extreme prevalence of coronavirus, it was relatively easy to find volunteers who became infected with coronavirus in everyday life (which is a necessary precondition to test effectiveness of the vaccine). Finding volunteers can take years if vaccines covering less common diseases are being developed. In this case, the process was much faster.


- Some companies have started production of vaccines even before obtaining an ultimate, final approval, which put them at risk. Thus, the vaccines can get to the market much faster after the approval. Should the vaccines not be approved, they will be discarded.


- Large number of people is being vaccinated around the world in a short time. Therefore, even rare side effects will be detected very quickly (vaccination is already taking place in the USA, Great Britain and across the EU)

- Development of COVID-19 vaccine followed up the research and development of MERS vaccine, also caused by coronavirus.

There are risks with the COVID-19 vaccine, as with any other vaccination. Our health is the most important thing we have, so we need to talk openly about the advantages and disadvantages of vaccination.

In the case of vaccination against COVID-19, the risks are much smaller if compared with huge benefits vaccines give us, because they enable us to gradually return to the normal way of life we are used to and look forward to.



  • Vaccination of the majority of the population will potentially save thousands of lives in Slovakia alone
  • Hospitals could be freed from thousands of COVID-19 patients.
  • Long-term consequences following the disease could be prevented in many cases.
  • It will enable gradual return to a normal life
  • In conclusion, an effective vaccine represents huge medical, social and economic benefit which can save us lot of lives, suffering and money.



Mild side effects: may vary with each type of vaccine, mostly described
 as pain in injection site, muscle pain, fever, or tiredness.


Such side effects can be relatively common, should be given some consideration and may be unpleasant. However, these are predictable side effects, should be taken into account, but it is nothing serious and causes short-term discomfort at the most.


Serious adverse reactions are closely monitored during clinical trials and their rarity is a core predicament for the vaccine to be approved.


Very rare side effects (occurrence of less than 1/10,000 people) may not be detected during clinical trials and may occur after the vaccine is registered. There is mechanism available for drug regulatory authorities to detect and eliminate them early.


Long-term side effects: these, of course, cannot be monitored during clinical trials, but our knowledge can be based on previous experience: no long-term side effects caused by vaccines approved by European Medicines Agency have been detected so far.

Currently, as many as 82 vaccines have been registered in Slovakia. However, neither of them has been deregistered due to side effects occurring later.

Should there be billions of people around the world vaccinated, cases of serious side effects will occur and will be made public. There are two things to be considered in such reports: Has a clear relation to vaccination been proved? What is the statistical probability of a more serious side effect?

Individual stories may sound bad, but they need to be compared to the 1.6 million COVID-19 deaths worldwide. Due to the existence of very rare serious side effects, a debate on the compensation fund arose.

Mortality of COVID-19 is the most frequently discussed issue, however, long-term adverse effects some people suffer after recovery are also important. It is well-know that Covid causes long-term problems and that too makes it dangerous.

On the contrary, there is no reason to worry about long-term side effects in case of COVID vaccines. All side effects described in the Pfizer vaccine package leaflet are short-term. Long-term side effects related to vaccines are generally rare.

As of 1 February 2021, the State Institute for Drug Control (ŠÚKL) registers 453 suspected adverse reactions in relation to vaccination against COVID-19. ŠÚKL has received 441 reports and 12 reports were sent to the European database to the holders. Twenty-five reports out of the total number have been evaluated as serious.

Until now, 450 of reported suspicion on side effects concerned Corminaty vaccine produced by Pfizer/BioNTech nad 3 reports concerned COVID-19 vaccine Moderna. However, it must be understood, that vaccine by Moderna has only been used since the end of January.

Vaccines designed to prevent COVID-19 are administered by a muscular injection and may cause reactions within hours or days of administration. Reported suspicions of adverse reactions are common and consistent with known adverse reactions that are also listed in the product documentation. ( )

The most commonly reported adverse reactions are short-term and not serious. These include pain in injection site, which may develop into pain in shoulder or limb to which the vaccine has been given, fever and even high fever, cold fever and chills, headache, muscle and joint pain, weakness, fatigue, nausea and others. Such reports are range from mild to moderate in intensity and disappear within a few days from administration of the vaccine.

Examples of reported suspected serious adverse reactions are allergic reactions, pre-collapse, syncope, thrombosis, and anaphylactic reaction. Such reactions were considered severe and required medical treatment. Patients recovered after receiving medical care.

The national institute has also been reported one death. The report concerned an elderly patient (79) with several chronic diseases, which were determined by autopsy as the main cause of death. Other mild side effects after vaccination - fever and weakness - also contributed to the overall deterioration of this patient's health. The causal link between vaccination and death was therefore assessed as possible.

Among the serious reports, there were also 6 suspicions of vaccine ineffectiveness. These reports were sent directly to the marketing authorization holder (Pfizer), while casualty and severity of reactions developed shall be assessed by the authorisation holder itself. Reports indicate that patients showed a positive result of an antigen/PCR test after first administration of the vaccine, with occupational exposure of patients to COVID-19. Considering the first dose of vaccination, the time interval between vaccination and test positivity, patients were not expected to develop a complete immune response against COVID-19. For these reasons, it is not possible to consider these cases as a vaccination failure.

The State Institute for Drug Control has not yet identified any unexpected reactions that would question the effectiveness of vaccines. The safety profile of vaccines to prevent COVID-19 is also reviewed at monthly intervals at European Union level, while the first safety analysis of Comirnaty has already taken place. As it has been shown at the European level, the safety profile of the vaccine is in compliance with the drug documentation and benefits of the vaccine highly outweigh any potential risks.

Do you know how to report suspected vaccine side effects?


Complications after vaccination are defined as vaccination side effects reaching beyond the normal scope of vaccination response with significant impact on health of the person being vaccinated. However, no side effects such as severe autoimmune reactions or severe neurological complications associated with vaccination have been reported in large pre-approval clinical trial after administration of mRNA vaccines.

As with all currently available vaccines, it is not possible to preclude the possibility that in very rare cases a hypersensitivity reaction (immediate allergic reaction, even shock) or other complications may occur. Should any symptoms exceeding the above mentioned temporary, local or general reactions occur after vaccination, please, contact your doctor.

(read the package leaflet for Comirnaty vaccine issued by Pfizer/BioNTech)

(please, read the vaccine package leaflet issued by Moderna)

(please, read the vaccine package leaflet for  COVID-19 Vaccine AstraZeneca)

Influenza deaths and COVID-19 deaths tend to be compared incorrectly.

However, these figures should not be compared as they are based on very different methodologies.

So, what do we compare? Calculation of excessive number of deaths related to respiratory symptoms (i.e., not only influenza) during the months of influenza epidemic (without virological confirmation of the pathogen), represents a statistical estimate of the overall impact of influenza and other respiratory disease including direct as well as indirect consequences of infulenza virus.

In our country, deaths from Covid-19 are reported on the basis of an autopsy with positive virological finding of CoV-2, which confirms that the primary cause of death was COVID-19. So, these are very accurate numbers, not estimates from statistical assumptions or modelling.

These numbers may be compared with the number of influenza deaths reported by the Public Health Office: during the 2018/2019 influenza season, the influenza virus was confirmed in 40 deaths.

More than 2 million people have died worldwide from COVID-19, despite actions taken in countries around the world. This number is still growing. According to the WHO, the actual number of deaths will be even higher than the officially recorded number of deaths (testing is still insufficient in many parts of the world and not all of those who died from COVID-19 were tested - many did never enter statistics).

The exact reason why there is so much attention paid to this virus is a huge difference between countries which cannot handle the situation and those, that can get the virus under control.

Uncontrolled spread of the virus can quickly overwhelm the healthcare system and cause much more damage. With rapid exponential growth, the line between almost empty hospitals and the moment when they get full, is very thin.

Insidiousness of corona virus lies in the fact that it is often invisible. Some infected people have no symptoms, feel healthy, and therefore may become carriers ("I don't need a face mask, I'm healthy"). It is inconspicuous, and this is the main weapon of this virus and that is why it spreads so massively.

Several studies confirm that many people have long-term problems even after they recover from the acute disease. According to a study by a research team from a hospital in Hradec Králové, up to 49 % of the 79 surveyed patients suffered problems even three months after recovery. Thirty percent of patients had lung structure disorders.

Vaccination represents the most effective means to fight against the virus and gradually slow down or stop the spread of COVID-19 and return to normal life.

(Read also Why Vaccination is the best way to get rid of COVID-19)