Given the spread of vaccines, several contagious and dangerous diseases have disappeared almost completely or become very rare. This is one of the reasons behind the significant increase in life-expectancy that occurred in the 20th century, and this also implicates the great importance of conducting research on contagious diseases and continuously developing vaccines in order to keep pace with the newly emerging infectious diseases.
Several pathogens, against which vaccines are available, are constantly present in our environment, but since personal and herd immunity have developed against them, they cannot cause large-scale infections and pandemic. If we stop immunization against these infections, they will reoccur (for further information, see: Preventable diseases by vaccination).
With the emergence of COVID-19, vaccine development has started at many parts of the world. Vaccines help the immune system (the natural defence system of the body) to produce antibodies and develop immune cells against the virus, thereby creating immunity against COVID-19. A mutual feature of vaccines is that they contain one or more non-infectious protein particulates (also known as antigens) of the virus that initiate the body’s defence mechanisms. However, different types of vaccines use differing methods to administer these antigens into the body.
General features of COVID-19 vaccines
Traditional vaccines contain these proteins/antigens - in the form of inactivated viral particulates. Newer vaccines introduce the genetic code of the viral spike protein to the body, with the help of a virus vector or in the form of transcriptional material (messenger ribonucleic acid - mRNA).
Like other vaccines, COVID-19 vaccines do not provide 100% protection against the infection. The efficacy of vaccines may vary depending on personal traits and the variations of the pathogen that occurs with time. Their efficacy is therefore measured by the prevalence of severe infections, the need for hospitalization and the number of deaths.
Since the beginning of the pandemic and the vaccination program, it has been concluded that any type of authorized COVID-19 vaccine helps to develop specific immunity against the infection, the probability of developing severe symptoms and the need for hospitalization are significantly decreased. Scientific data collection on the length of immunity has been continuously performed. Based on the first experiences (the first one and a half year) of the vaccination program, it can be stated that six months after the primary series vaccination (for further details, scroll down), an additional, so-called booster vaccine (that helps to enhance or restore protection that might have waned over time) is necessary.
For further information, read: Booster vaccines for COVID-19
Booster vaccines are not unique in the field of COVID-19, several personal and environmental factors may contribute to the need for booster vaccines. Such factors are limited immune memory (the immune system’s memory declines with aging), or the changes in the pathogens’ properties (see: COVID-19 variants). At a rough estimate, the human immune system can develop permanent immunity against 1000 antigens of pathogens or foreign material – which means an average 30 new antigens in a year. For this cause, several vaccines perform the most effectively when administered in childhood. If administered to an adult who has general health conditions, the probability of developing permanent immunity is lower.
Vaccines available in Hungary
In Hungary, currently the six COVID-19 vaccines are available, which can be classified as the the followings:
mRNA vaccines
The mRNA COVID-19 vaccine is an information delivering system. The mRNA contains encoded information on the constitution of the coronavirus’s (SARS-CoV-2) spike protein that is present on the viral surface. By introducing the mRNA into the body by vaccination, the mRNA “gives instructions” to the neighbouring cells to produce the spike protein. After this, the immune system recognizes spike proteins as antigens, and starts producing antibodies against it – this is how the immune response develops.
The purpose of the mRNA COVID-19 vaccines is to make the immune system familiar with the spike protein without actually introducing the virus itself to the body, and thereby preparing the immune system for a future infection. Hence, in case of an actual infection, the body will overcome the infection more easily, and the disease will not develop, or develops only in a milder form, compared to the one that develops for the first infection in unvaccinated patients.
Currently two mRNA vaccines are available:
Pfizer-BioNTech (COMIRNATY)
- primary series vaccination: 2 vaccines,
- available for everyone ages 5 years and older,
- available for patients with chronic diseases.
Moderna
- primary series vaccination: 2 vaccines,
- available for everyone ages 6 years and older,
- available for patients with chronic diseases.
Virus vector vaccines
Virus vector vaccines make the body’s own cells to produce viral proteins. In case of the COVID-19 virus (SARS-CoV-2) this viral protein is the spike protein present on the viral surface. In virus vector vaccines the carrier vectors that “carry” the genetic code of the spike protein are non-infectious adenoviruses, that -after being administered into the body- “give commands” to the immune cells of the body for spike protein production. Hence, the immune system recognizes the produced spike proteins as antigens and starts producing antibodies against it - this is how the immune response develops.
The purpose of the COVID-19 virus vector vaccines is to make the immune system familiar with the spike protein without actually introducing the virus itself to the body, and thereby preparing the immune system for a future infection. Hence, in case of an actual infection, the body will overcome the infection more easily, and the disease will not develop, or develops only in a milder form, compared to the one that develops for the first infection in unvaccinated patients.
Currently available virus vector vaccines:
AstraZeneca
- primary series vaccination: 2 vaccines,
- available for everyone ages 18 years or older,
- it can be administered to patients with chronic diseases, if their diseases are managed properly.
Sputnik V
- primary series vaccination: 2 vaccines,
- available for everyone ages 18 years or older,
- it can be administered with precaution to people with certain types of chronic diseases.
Johnson&Johnson’s Janssen
- primary series vaccination: 1 vaccine,
- available for everyone ages 18 years or older,
- it can be administered to patients with chronic diseases if there is no other contraindication.
Vaccines containing inactivated viruses
When vaccinating someone with a vaccine that contains an inactivated virus, an inactivated (killed) coronavirus is administered into the body. The inactivated virus cannot develop a disease, but the immune system reacts the same way as it has met the virus that is capable of developing the disease.
The purpose of the COVID-19 vaccines containing inactivated virus is to make the immune system familiar with the surface proteins of the virus without actually introducing the virus itself to the body, and thereby preparing the immune system for a future infection. Hence, in case of an actual infection, the body will overcome the infection more easily, and the disease will not develop, or develops only in a milder form, compared to the one that develops for the first infection in unvaccinated patients.
The vaccine containing inactivated virus:
Sinopharm
- primary series vaccination: 2 vaccines,
- available for everyone ages 18 years and older,
- it can be administered for patients with chronic diseases, if their diseases are managed properly.
Like other vaccines or medications, COVID-19 vaccines may produce mild side effects or adverse events (allergy, pain at the site of vaccination, subfertility, transient fatigue), which are the natural symptoms of the immune response and resolve quickly (For further information: Adverse events and side effects of vaccines). For further information on possible side effects, read the official patient information leaflet or contact your GP or the doctor in charge of your vaccination.
For further information on vaccines:
Pfizer-BioNTech (COMIRNATY) COVID-19 vaccine
Moderna COVID-19 vaccine
AstraZeneca COVID-19 vaccine
Johnson&Johnson’s Janssen COVID-19 vaccine
Sputnik V COVID-19 vaccine
Sinopharm COVID-19 vaccine
For information on the necessary booster vaccinations, read the following artice.
Since vaccinated patients can also get infected with coronavirus (especially in situations where the viral load is high – e.g. at workplaces), therefore, it is important to comply with the currently prevalent hygienic and other protective measures, such as cleaning the hands or wearing masks. These measurements are set out by prevailing legal regulations. For further information on General protective measures, read the applying article.
