Vaccination

Vaccination is one of the most important ways to prevent infectious diseases in modern medicine. Vaccines help the body prepare for contact with a specific infectious agent — a virus or bacterium — before a person is actually exposed to it. After vaccination, the immune system learns to recognise the infectious agent and, when encountering it in the future, can respond faster and more effectively. As a result, vaccination can protect against disease, reduce the risk of severe illness, complications and death, and help limit the spread of infections in society.

Vaccination is not intended only for children. It is also important for adults, seniors, pregnant women, people with chronic diseases, healthcare and social care workers, travellers and people at increased risk of infection. Some vaccines are received in childhood, but for certain infections protection decreases over time and a booster dose, or revaccination, is needed.

The purpose of vaccination is not only to avoid mild illness. Many infections against which vaccination is available can cause severe complications, hospitalisation, long-term consequences or death. This is why vaccination is both an individual health protection measure and a public health measure.

What is vaccination?

Vaccination is a medical preventive procedure during which a vaccine is introduced into the body. The purpose of a vaccine is to introduce the immune system, in a safe and controlled way, to a specific infectious agent or part of it, so that the body can develop a protective response before real infection occurs.

A vaccine does not contain the disease in the form in which a person would usually become infected naturally. Depending on the type of vaccine, it may contain an attenuated or inactivated infectious agent, a purified part of it, a harmless form of a toxin, a protein, a polysaccharide, a viral vector or genetic instructions that temporarily help the body produce an antigen. The immune system recognises this antigen and begins to build protection.

In everyday language, terms such as “jab”, “injection” and “vaccination” are often used. The medically more precise term is “vaccination”, but these terms are usually used with a similar meaning — the administration of a vaccine to create protection against a specific infectious disease.

Vaccination and immunisation — are they the same?

In everyday language, the words “vaccination” and “immunisation” are often used as synonyms, but there is a slight difference between them. Vaccination is the procedure of administering a vaccine. Immunisation is the process by which the body gains protection against a specific infection.

Most often, immunisation occurs after vaccination, but immunity can also develop after an infection. However, having the disease is not a safer or preferable way to gain protection, because the course of an infectious disease can be unpredictable and may sometimes cause serious complications.

How do vaccines work?

The immune system is able to remember infectious agents. When a person first encounters a virus or bacterium naturally, the body needs time to recognise the threat and develop a sufficiently strong protective response. During this time, the infection may spread and cause symptoms and complications.

Vaccination allows the immune system to prepare in advance. After a vaccine is administered, the body recognises the antigen in the vaccine or the information given to the immune system and begins to develop a protective response. Antibodies and immune memory cells are formed. If the person later encounters the actual infectious agent, the immune system can respond faster and more effectively.

For some vaccines, one dose is sufficient, while others require several doses to achieve an adequate and long-lasting immune response. Some vaccines later require booster doses because protection may decrease over time or the infectious agent may change.

Why is vaccination important?

Vaccination protects not only the individual person but also society as a whole. The larger the proportion of people vaccinated against a contagious infection, the harder it is for the infectious agent to spread. This is especially important for people who cannot receive certain vaccines for medical reasons, for example due to severe immunosuppression or specific contraindications, as well as for infants who have not yet reached the age at which vaccination is possible.

Vaccination also helps reduce the burden on the healthcare system. Outbreaks of infectious diseases can cause a rapid increase in patient numbers, hospitalisations, complications and long-term consequences. Vaccination programmes help prevent many diseases that were once a common cause of severe complications or death.

It is important to understand that infectious diseases can return if vaccination coverage in society decreases. This is especially true for highly contagious diseases such as measles. Even if a particular disease is currently rare in Latvia, it may be imported from other countries and spread among unvaccinated or incompletely vaccinated people.

Which diseases are vaccinated against?

The vaccination schedule may differ from country to country, as it is determined by the spread of infections, public health priorities, available vaccines and national recommendations. In Latvia, information on the childhood vaccination schedule and state-funded vaccines is published by the Centre for Disease Prevention and Control, while an individual vaccination plan for a child or adult can be assessed by a family doctor, paediatrician, infectious disease specialist or another specialist.

Children are usually vaccinated against several infections, such as tuberculosis, hepatitis B, diphtheria, tetanus, whooping cough, poliomyelitis, Haemophilus influenzae type b infection, pneumococcal infection, rotavirus infection, measles and rubella, mumps, chickenpox and human papillomavirus. The specific timing of vaccination, number of doses and intervals should be assessed according to the current Latvian vaccination schedule.

Vaccination is also important for adults. Some vaccines received in childhood provide long-lasting protection, while others require repeated doses. Adults should pay particular attention to checking their vaccination status against diphtheria and tetanus, as well as considering vaccination against influenza, Covid-19, tick-borne encephalitis, pneumococcal infection, hepatitis, HPV, whooping cough and other infections depending on age, health status, occupation, travel plans and risk factors.

Mandatory, state-funded and recommended vaccination

In Latvia, the vaccination procedure is determined by legislation and the national immunisation programme. In everyday language, patients often use the terms “mandatory vaccination”, “state-funded vaccination” and “recommended vaccination”, but these concepts are not exactly the same.

State-funded vaccines are those provided to certain population groups from the state budget, for example within the childhood vaccination schedule or for specific risk groups. This means that a particular vaccine is paid for at a certain age or for a particular patient group because its benefit is especially important from a public health perspective.

Recommended vaccines are vaccines that a doctor may recommend, taking into account a person’s age, health status, occupation, lifestyle, travel plans or increased risk of infection. Some of these may be paid vaccines, while in other cases they may be funded for specific risk groups or under certain circumstances.

It is important to understand that the purpose of vaccination is not only to formally follow a schedule. Its purpose is to protect a person from diseases that can cause severe complications, long-term consequences or death. Therefore, the vaccination status of both children and adults should be assessed practically: which vaccines have been received, which doses have been missed, whether a booster dose is needed and whether the person has individual risk factors.

Vaccination in children

The aim of childhood vaccination is to protect the child at a time when the immune system is still developing and some infections may be particularly severe. The vaccination schedule is designed so that protection develops before the child is exposed to an increased risk of infection. Therefore, vaccines are not scheduled randomly — their timing is linked to the child’s age, the immune system’s ability to respond and the risks of specific infections.

In infants and young children, some infections can cause a more severe course of disease than in adults. For this reason, early vaccination is particularly important. The vaccination schedule helps ensure that a child receives protection at the time when it is most needed.

Parents should keep the child’s vaccination records and regularly discuss vaccination status with the family doctor or paediatrician. If a vaccination has been missed, this does not always mean that vaccination must be started again from the beginning. A doctor can create an individual catch-up or continuation vaccination plan.

Vaccination in adults

Adults often assume that vaccination applies only to children, but this is not correct. In adulthood, protection against some infections may decrease, while health status, working environment, travel habits and contact with risk groups may change.

The need for vaccination may differ between a healthy young adult, a pregnant woman, a senior, a healthcare worker, a person with chronic disease or a patient with weakened immunity. In adults, the vaccination plan should be assessed individually.

A doctor can check when a booster dose against diphtheria and tetanus is needed, whether the necessary doses against measles, rubella and mumps have been received, and when vaccination against tick-borne encephalitis, influenza, Covid-19, pneumococcal infection, hepatitis, HPV or other infections is needed.

Special attention to vaccination status should be paid by people working in healthcare, social care, educational institutions, childcare, with animals, in laboratories or in other environments where the risk of infection may be increased.

Vaccination during pregnancy

During pregnancy, vaccination issues should be assessed especially carefully, because the aim is to protect both the pregnant woman and the baby. Some infections may have a more severe course during pregnancy or pose a risk to the foetus and newborn. Therefore, certain vaccines may be especially important during pregnancy.

Some vaccines may be recommended during pregnancy, for example in certain situations vaccination against influenza or whooping cough, because these infections can be dangerous for the pregnant woman and the newborn. Live attenuated vaccines, however, are generally not used during pregnancy unless there are special circumstances and a doctor’s decision.

If a woman is planning pregnancy, it is advisable to check her vaccination status in advance, especially against rubella, chickenpox and other infections that may pose a risk to the foetus during pregnancy. Individual recommendations are best provided by a family doctor, gynaecologist or infectious disease specialist.

Vaccination in seniors and people with chronic diseases

In seniors and people with chronic diseases, infections may more often have a severe course. A higher risk of complications may occur in patients with cardiovascular diseases, diabetes, chronic lung diseases, kidney diseases, liver diseases, oncological diseases or weakened immunity.

In such cases, vaccination can be particularly important because it reduces the risk of severe disease, hospitalisation and complications. For example, influenza, pneumococcal infection, Covid-19 or tick-borne encephalitis may have a much more severe course in some patients than in healthy adults.

However, in patients with serious chronic diseases or immunosuppressive therapy, the vaccination plan must be adjusted individually. Sometimes a specific vaccine type must be selected, a particular interval before or after treatment must be observed, or live vaccines must be avoided. In such cases, a doctor’s consultation is necessary.

Travel vaccination

When travelling to other countries, a person may come into contact with infections that are rare or not present in Latvia. Therefore, before travelling, it is advisable to check both basic vaccination status and the vaccines required or recommended for the specific destination.

Travel vaccination may be needed against hepatitis A, hepatitis B, typhoid fever, yellow fever, meningococcal infection, rabies, poliomyelitis, Japanese encephalitis or other infections, depending on the destination, duration of travel, season, living conditions, planned activities and individual health status.

Travel vaccination should not be postponed until the last moment. Some vaccines require several doses or time for sufficient protection to develop. It is best to consult a doctor several weeks before the planned trip. In the case of more complex routes, tropical countries or high-risk travel, a consultation with an infectious disease specialist or travel medicine specialist may be necessary.

Types of vaccines

Vaccines can be different, and their mechanisms of action vary. The main types of vaccines are live attenuated vaccines, inactivated vaccines, subunit and recombinant vaccines, polysaccharide and conjugate vaccines, toxoid vaccines, mRNA vaccines and vector vaccines.

Live attenuated vaccines contain a weakened infectious agent that usually does not cause disease in a person with a normal immune system, but helps create a strong immune response. This type of vaccine may not be suitable for people with significantly weakened immunity or for pregnant women.

Inactivated vaccines contain a killed infectious agent or parts of it. They cannot cause the corresponding infection because the agent is not alive. Some inactivated vaccines require several doses or booster doses.

Subunit, recombinant and polysaccharide vaccines contain specific components of the infectious agent, such as proteins or capsule components. They help the immune system recognise important parts of the infectious agent without introducing the whole microorganism.

Toxoid vaccines protect against the effects of bacterial toxins, for example in diphtheria or tetanus. Such vaccines help the body develop protection against the toxin that causes the most severe manifestations of the disease.

mRNA and vector vaccines provide the body with instructions to temporarily produce an antigen against which the immune system develops a protective response. These vaccines do not change a person’s genetic material and do not cause the corresponding infectious disease.

The type of vaccine affects how many doses are needed, who the vaccine is suitable for and in which situations special caution is required.

What happens before vaccination?

Before vaccination, a healthcare professional usually clarifies which vaccine is needed, whether the person has an acute illness, high temperature, a history of severe allergic reactions or a previous serious reaction after vaccination. Age, pregnancy, chronic diseases, the state of the immune system and medicines being used are also taken into account.

This assessment is important because vaccination is safe for most people, but in certain situations the type of vaccine or the timing of administration must be adjusted individually. It is especially important to inform the doctor before vaccination if the person has had anaphylaxis, a severe allergic reaction after a previous vaccine dose, is receiving immunosuppressive therapy, is undergoing cancer treatment, has had an organ transplant, is pregnant or has a serious autoimmune disease.

In some cases, a consultation with a family doctor, paediatrician, gynaecologist, infectious disease specialist, allergist or treating specialist may be required before vaccination. This does not mean that vaccination is impossible. It is often still recommended, but the most appropriate time, vaccine type and safest vaccination plan must be selected.

How to prepare for vaccination?

Before vaccination, it is advisable to check which vaccine is planned, whether several doses are needed and when the next dose should be received. A personal identification document and vaccination records, if available, should be brought to the vaccination appointment.

Before the vaccine is administered, the healthcare professional should be informed about acute illnesses, fever, allergies, previous reactions after vaccines, pregnancy, chronic diseases and medicines being used.

No special preparation is usually required. It is not recommended to take antipyretic or anti-inflammatory medicines preventively without a doctor’s instruction if there are no symptoms. After vaccination, the instructions given by the doctor or nurse should be followed.

When should vaccination be postponed?

Vaccination may need to be postponed if a person has an acute illness with moderate or severe deterioration of wellbeing, a high temperature or unclear symptoms. Mild nasal congestion or a minor cold is not always a reason to postpone vaccination, but the decision is made by a doctor after assessing the specific situation.

Sometimes the timing of vaccination must be adjusted according to medication use or a course of treatment, for example in the case of immunosuppressive therapy, chemotherapy or biological medicines. In such cases, the vaccination plan should be prepared together with the treating doctor.

Postponing vaccination is not the same as refusing vaccination. If vaccination is temporarily unsuitable, the doctor can advise when it can be carried out safely later.

What should you do if vaccination has been missed?

If vaccination has been missed, you should contact your family doctor, paediatrician or vaccination clinic. Vaccination can usually be continued according to an individual schedule rather than started again from the beginning. This applies to both children and adults.

Missed vaccination should not be ignored. Incomplete vaccination may mean insufficient protection against infection. A doctor can check which doses have been received, which are missing, what intervals must be observed and whether additional doses are needed.

If vaccination records have not been kept, the doctor can assess the situation and recommend the next steps. In some cases, antibody testing may be possible, but this approach is not necessary or sufficient for practical decision-making for all infections.

Does vaccination always provide complete protection against illness?

No vaccine provides 100% protection for every person. However, in vaccinated people, infection often does not occur at all or has a milder course. The main purpose of vaccination is to reduce the risk of severe disease, complications and death.

Some vaccines provide very high protection against infection, while for others the main benefit is prevention of severe disease. Vaccine effectiveness is influenced by a person’s age, immune system status, vaccine type, number of doses received, time since the last dose and the characteristics of the infectious agent.

For this reason, some vaccines require booster doses. For certain infections, such as influenza, the vaccine composition is regularly adjusted because viruses change.

What is a booster dose or revaccination?

A booster dose, or revaccination, is an additional vaccine dose that helps restore or strengthen protection. It is needed for vaccines whose immunity may weaken over time.

For example, adults need periodic renewal of protection against diphtheria and tetanus. Vaccination against tick-borne encephalitis, influenza, Covid-19 and other infections also requires a specific repeated-dose schedule.

The need for a booster dose does not mean that the vaccine “does not work”. It is a normal part of vaccination strategy when protection decreases over time or the infectious agent changes.

What is herd immunity?

Herd immunity means that an infection has greater difficulty spreading in society because a sufficiently large proportion of people are immune — after vaccination or previous infection. This reduces the chance of transmission also for those who are not protected themselves or cannot be vaccinated.

Herd immunity is especially important for highly contagious diseases, such as measles. If vaccination coverage decreases, collective protection weakens and the risk of outbreaks increases.

However, herd immunity is not equally effective for all infections. Its role depends on how contagious the disease is, vaccine effectiveness, duration of protection and whether the infection can also spread from people without symptoms.

Vaccination and natural infection — which is safer?

Some people believe that it is better to “naturally catch” an infection rather than be vaccinated. However, the course of infection can be unpredictable. Even in apparently healthy people, some infections can cause severe complications, hospitalisation, long-term consequences or death.

Vaccination allows the immune system to prepare while avoiding the risks of the full disease. For example, measles can cause pneumonia, encephalitis and other serious complications; influenza can be dangerous for seniors, pregnant women and people with chronic diseases; HPV infection can be associated with the risk of cervical and other cancers; hepatitis B can become chronic and damage the liver.

Natural infection is not a controlled form of prevention. Vaccination is intended to help the immune system gain protection with a much lower risk than the infection itself.

Do vaccines overload the immune system?

Vaccines do not overload the immune system. A person’s immune system encounters many microorganisms and antigens every day in the environment, in food and on the skin. The amount of antigen in vaccines is controlled, and the vaccination schedule is designed so that vaccines are safe and effective at a specific age.

If several vaccines are administered during one visit, this is usually done according to tested recommendations. This approach helps a child or adult gain protection sooner and reduces the number of visits needed.

Are vaccine additives dangerous?

Vaccines may contain additives that help ensure vaccine stability, sterility or a better immune response. The amount of these substances in vaccines is very small and regulated. Before a vaccine is approved for use, not only the active substance but also the full composition is assessed.

If a person has a known allergy to a specific vaccine component, the doctor must be informed before vaccination. Allergy to vaccine components is one of the reasons why a brief health and medical history assessment is carried out before vaccination.

Vaccination records and checking vaccination status

Vaccination status can be checked using a child’s vaccination record, medical documentation, family doctor records or electronic health system data, if available. If records are missing or incomplete, the doctor can assess the situation and recommend the next steps.

Vaccination documentation is important not only in childhood. It may also be needed in adulthood, for example when starting work in certain professions, travelling, planning pregnancy, treating chronic diseases or assessing the need for booster vaccination.

Can a person be vaccinated while taking medicines?

Many everyday medicines are not an obstacle to vaccination. However, the doctor should be informed about all medicines, especially if a person is taking medicines that suppress the immune system, biological therapy, chemotherapy, long-term corticosteroids or medicines after organ transplantation.

In such cases, the vaccine type and timing of administration can be very important. Sometimes vaccination is recommended before starting therapy, while in other cases a specific interval between medication use and vaccination must be observed. The decision is made by the treating doctor or infectious disease specialist.

Vaccination and allergies

Allergies by themselves do not always mean that a person cannot be vaccinated. For example, seasonal allergies, allergic rhinitis or mild food allergies are usually not automatic contraindications.

However, a severe allergic reaction after a previous vaccine dose or a known allergy to a vaccine component is a serious reason to assess vaccination individually. Before vaccination, the doctor should be informed about any previous severe allergic reactions.

If a person has had anaphylaxis or a complex allergy history, vaccination may need to be planned in a medical institution where observation and rapid help are available if needed.

Vaccination and autoimmune diseases

In patients with autoimmune diseases, vaccination is often especially important because infections can trigger disease flare-ups or have a more severe course, especially if immunosuppressive therapy is being used. However, the vaccination plan must be adapted to disease activity and treatment.

Live vaccines may not be suitable for some patients, while inactivated vaccines can often be administered safely. The decision should be made together with the treating doctor. It is advisable to discuss vaccination in good time, especially before starting immunosuppressive therapy.

Common myths about vaccination

One of the most common myths is the belief that infections against which vaccination is given no longer exist. In reality, many of them are rarer precisely because of vaccination. If vaccination coverage decreases, diseases can return and cause outbreaks.

Another myth is the belief that vaccines always cause severe side effects. In reality, serious reactions are rare, while mild and short-term reactions are relatively common and usually not dangerous. Vaccine safety is continuously monitored.

Some people believe that it is better to postpone a child’s vaccination or choose a “slower” schedule. However, the vaccination schedule is designed so that the child receives protection at the time it is needed. Unjustified postponement of vaccination prolongs the period during which the child is vulnerable to infections.

Another common belief is that vaccines cause autism. Scientific data do not support such a link. This myth arose from long-discredited claims that do not correspond to modern evidence.

When should you consult an infectious disease specialist?

A family doctor is usually sufficient for routine vaccination planning. A consultation with an infectious disease specialist may be necessary in more complex situations — if vaccination status is unclear, there has been a severe reaction after a vaccine, there is immunosuppression, oncological disease, organ transplantation, HIV infection, autoimmune disease, pregnancy planning with unclear vaccination history, a complex travel vaccination plan or a need to assess risks and benefits individually.

An infectious disease specialist can help create an individual vaccination plan, assess contraindications, choose the most suitable vaccine type, plan vaccination before travel or before immunosuppressive therapy, and help patients who have concerns after previous reactions.

Summary

Vaccination is a safe, tested and effective method of preventing infectious diseases. It helps protect people from many serious diseases, reduces the risk of complications and limits the spread of infections in society.

Vaccination is not relevant only for children. It is also important for adults, seniors, pregnant women, people with chronic diseases, travellers and patients at increased risk of infection. The need for vaccination differs depending on age, health status, vaccines previously received, occupation, lifestyle and travel plans.

Therefore, it is best to discuss vaccination status and the future plan with a family doctor, paediatrician, infectious disease specialist or another healthcare professional. In more complex cases, an individual vaccination plan helps ensure that the patient receives protection at a safe and appropriate time.

This information is intended for informational and educational purposes only. It does not replace medical consultation, diagnosis or treatment. Self-diagnosis and self-treatment may be incorrect, so questions about vaccination, contraindications, chronic diseases, pregnancy, childhood vaccination or travel vaccination should be discussed with a family doctor, infectious disease specialist, paediatrician, gynaecologist or another relevant specialist. In the event of a severe allergic reaction, breathing difficulties, rapid deterioration of wellbeing, seizures or other high-risk symptoms, emergency medical help should be sought immediately.

References and authoritative sources

• Centre for Disease Prevention and Control: Vaccination
• Centre for Disease Prevention and Control: Vaccination schedule
• National Health Service: Childhood vaccination
• World Health Organization (WHO): Vaccines and immunization
• World Health Organization (WHO): Vaccine safety
• European Centre for Disease Prevention and Control (ECDC): Immunisation and vaccines
• European Centre for Disease Prevention and Control (ECDC): Vaccine Scheduler
• Centers for Disease Control and Prevention (CDC): General Best Practice Guidelines for Immunization
• Centers for Disease Control and Prevention (CDC): Contraindications and Precautions

Consulted by

• Infectologist and hepatologist Prof. Angelika Krūmiņa
• Infectologist, resident physician Vladimirs Morozovs