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And so, the war has begun. COVID-19 vaccines

29/01/2021 Epidemiology

Existing Vaccines

To date, there are about 10 vaccines in the race against COVID-19 (including those from Janssen and Novavax laboratories), of which there are 2 vaccines authorized for use by the CDC (Centers for Disease Control and Prevention) and the FDA (Food and Drug Administration) of the United States of America:

  • BNT162b2 from Pfizer-BioNTech.
  • mRNA-1273 from Moderna.

Additionally, there is the Russian vaccine called Sputnik V from the Gamaleya Institute and the AZD1222 from Oxford-AstraZeneca,


How do they work?

As you may remember, we explained in detail the principle of all vaccines in our blog Vaccines: The shield of the immune system”, What varies for the COVID-19 vaccine is the material that seeks to develop the immune response of the human body:

  • mRNA type. In this type, what is injected into the body is a small sample of the virus's protein material. In this material comes essentially instructions on how the crowns of the upper layer of the Sars-COV-2 virus, the responsible for COVID-19, are generated. Remember that the cell of this virus has crown forms ( hence its name coronavirus) which are those that connect with the cells of the body, thus getting through the internal genetic material to spread the disease.

Once the material has entered, the body "reads the instructions" and makes cells with virus-like crowns, without the virulent material. In this way, the body identifies them as a pathogen and creates the corresponding defense antibodies, which will remember how to fight the virus in the future.


  • Of Vector type.  These vaccines use a modified virus called "vector" whose reproductive ability is eliminated. This vector is injected with genetic material from another virus, so that it ends up serving only as a weakened vehicle or "broken car" to deliver the genetic material into the body without the risk of a real infection.

What has been sought to deliver in this "broken car" is specifically the material that causes the external crowns of the coronavirus, because it is precisely these crowns that facilitate the connection with our cells and thus disperse the infection.

From there, the functioning in the body is the same as the mRNA type, by identifying the genetic material, the body recognizes it as a pathogen and develops antibodies that will respond to a possible future threat.


So far, some IMPORTANT Data goes:

  • COVID-19 vaccines cannot cause the disease or any other infection. Remember that in no case is virulent material injected, only the material related to the outer layer of the Sars-COV-2 virus that connects to our cells is introduced, that is, material from the crowns.
  • None of these materials act with our DNA as they would in a real infection, just seeks to generate an immune response so that the body generates antibodies by memory and knows how to react against a real threat, if we are actually infected with the Sars-COV virus -2.
  • The method of obtaining the vaccine under the mRNA type is more recent than the vector type. When we talk about new ones, we are not talking about a 1-year job, but about studies that have been done for decades.
  • mRNA vaccines are relatively easier to build, allowing the development of vaccines to be much faster than other methods.
  • The technology developed for mRNA-type vaccines can make it possible to achieve protection against other diseases by reducing the number of injections needed for this.
  • In addition to dealing with mRNA technology for the development of vaccines, it has been involved in cancer research, also helping to develop a certain response of the immune system against specific types of cancer.


Are they safe?

No vaccine is 100% harmless in terms of allergic reactions, what is considered in favour is to consider that allergic reactions (moderate and severe type) do not exceed a minimum margin, making statistics generally favorable.

For this reason, the application of the vaccine is performed with a special protocol in which, once the injection has been received, the person is monitored on site for 15 to 30 minutes, waiting for some alarm data. Ideally, vaccine providers should have special equipment and medicines in place in case a severe reaction occurs.

The reactions generated by the application of COVID-19 vaccines are constantly being monitored and mild to severe allergic reactions have been identified.


Mild reactions:

There have been cases of people who have allergic reactions within 4 hours after vaccination, such as itching, swelling and difficult breathing, shown by a certain wheezing and/or noisy breathing, which occurs when the respiratory passages shrink.

The right thing to do in this case is to go to a hospital for general control and monitoring.


Severe reactions:

A severe reaction is considered “Anaphylaxis”, it is an acute and life-threatening allergic reaction, symptoms can range from skin rash, nausea, vomiting, difficulty breathing or shock. Immediate treatment is with epinephrine and the transfer to the emergency area as soon as possible.


This type of reaction usually occurs when you are highly allergic to a component, such as peanuts.


So, what can we expect when receiving a COVID-19 vaccine?

 As we have already explained, when receiving the vaccine, the body reacts by generating antibodies, which cause internal reactions:


In the arm where you are injected:

  • Pain
  • Swelling

  In the body in general:

  • Fever
  • Shaking chills
  • Decay
  • Headache

In the arm where you are injected:

  • Clean, cold cloths.
  • Move your arm.

In the body in general:

  • Drink lots of liquids.
  • Consult your doctor to take doses of ibuprofen or paracetamol.


See your doctor when the redness or tenderness where you were injected increases after 24 hours, or if the side effects don't go away after a couple of days.

In general, the side effects are similar to a strong flu, it is recommended to continue with calm and restful activities, reminding that the symptoms should be completely overcome after about 2 days.



  • At no time have the standards that COVID-19 vaccines must comply with under the safety protocols been transgressed or overlooked, even with different technologies, all have passed the corresponding safety filters.
  • We recommend that, if you have ever had allergic reactions in your life (whether medicines, food, or drinks), you consult your family doctor about the components of the COVID-19 vaccines and verify whether they recommend applying it to you.
  • If you have an allergic reaction at the time of application of the vaccine, it is recommended that you consult your doctor later to assess the second application. The CDC strongly recommends that the second dose should not be given to people who have reacted allergically to the first doses.


In our following blogs we will tell you one by one the details of the authorized vaccines.










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