Types of vaccines against COVID-19

In December 2020, with the first administration of the pfizer vaccine In the United States (USA), the main epidemiological strategy for the fight against the pandemic by

There has never been a comparable economic and regulatory effort in order to develop and approve vaccines for a new disease in record time. But, some changes on the indications, in parallel with new studies or findings, have made the population have illusion, hope, and also many doubts about the safety and effectiveness of vaccines.

Vaccines authorized by the European Medicines Agency (EMA)

Messenger RNA vaccines

• Pfizer-BioNTech (Comirnaty): very popular for the public opinion, the first approved and also a pioneer in having excellent efficacy and safety results for older groups (those with the highest risk), but which requires conservation at -70ºC, administration of two doses, and is priced higher than its competitors.
• Modern (mRNA-1273): American vaccine that requires storage at -20ºC and administration of two doses. It has been used mainly for residences in Spain.

Vaccines using an adenovirus as a vector

• Janssen or Johnson & Johnson (JNJ-78436735 or Ad26.COV2.S.): vaccine already in use in the USA. Its arrival in Europe is preceded by the thrombotic incidences being studied in adenovirus vaccines. It has the great advantage of requiring only a dose and good conservation in a traditional refrigerator (4ºC).
• AstraZeneca (Vaxzevria): It is the cheapest of all available in Europe. It can be stored at 4ºC. It is the one used in most countries in the world. But it requires two doses and at present it is the one that has raised the most news about its safety.

The Astrazeneca vaccine is safe. It is normal that with a well-functioning pharmacovigilance system, adverse effects are reported and that, given transparency and interest, these are a source of news. But the possible side effects are very rare and they have already been seen in other commonly used drugs. However, it is understandable that media attention from sources of diverse reliability magnifies and distorts the population's perception of safety and risk.

Other vaccines used to date outside of Europe

Adenovirus as a vector (such as AstraZeneca and Janssen)

They are also kept at 4ºC:

• Gamaleya (Sputnik): unlike the rest of the vaccines that use adenovirus, it uses a different one in each dose (Ad5 and Ad26).
• CanSinoBio: Chinese Ad5 vaccine that would only require one dose.

Inactivated virus

• Sinopharm and Sinovac Biotech of Chinese origin, and Bharat Biotech, of India. They must be kept at 4ºC and require 2 doses.

Peptides

• VECTOR (EpiVacCorona): Russian two-dose vaccine pending approval in Venezuela.

Does the AstraZeneca vaccine cause blood clots?

A autoimmune phenomenon, produced by the patient's own defenses, which have named Vaccine-Induced Immune Prothrombotic Thrombocytopenia (VIPIT) similar to the already known Heparin Induced Thrombocytopenia (HIT). It consists in that the person's antibodies agglutinate the platelets causing both the conglomerated platelets and the risk of bleeding due to the lack of these platelets for their normal functions.

This person would have symptoms evident between the fifth and ninth day after administration, such as a very severe headache or a feeling of shortness of breath, which may be accompanied by petechiae (red-purple dots) on the skin. An analysis could confirm the diagnosis and give a treatment.

ATTENTION! Having a moderate headache, muscle pain, and general ill feeling in the first two to four days after the vaccine is normal and does not have to scare us.

What if I have risk factors for thrombosis? What about other risk factors?

There is no relationship with any risk factor. The only thing that could be a risk factor is having had the rare reaction with heparin (a blood thinner widely used in medicine) already mentioned.

People at risk of thrombosis or other risk factors have the most reason to get vaccinated as soon as possible with whatever vaccine is available to them.

The covid-19 greatly increases the risk of habitual thrombosis and that is multiplied by other risk factors such as clotting pathologies, having had previous blood clots and even some as frequent as smoking, being pregnant, having varicose veins or taking contraceptives. None of this increases the risk with the vaccine.

Also, someone with significant risk factors for thrombosis suffering from covid-19 will likely receive anticoagulation to avoid high risk of thrombosis, usually with heparin. And as previously explained, heparin also carries this rare risk of immune thrombocytopenia.

 Getting vaccinated not only reduces individual risks of mortality and disease, it also protects the environment of those who are vaccinated and the society in which they live.

Why then did you change the vaccination age with AstraZeneca?

The first trials included very few patients older than 55 years, so Europe initially limited its use until that age. Later, when inoculating it to more people of other ages in other countries, it has also been shown to be effective for older people.

Given that older age groups have shown a much higher mortality rate with covid-19, while studies on health alerts are being completed, use has been limited to the age group in which the risk-benefit is greatest, although It is clear that it is generally favorable at other ages as well.

If you have any questions about vaccines, you can call the 24-hour Medical Guidance service available with the

CALCULATE YOUR PRICE

• The most advanced countries in percentage of vaccinated population are Israel and the United Kingdom.
• Having a moderate headache, muscle pain, and general ill feeling in the first two to four days after the vaccine is normal and does not have to scare us.
• The Astrazeneca vaccine is safe. It is the vaccine that more countries are using and today it has demonstrated efficacy and safety.

Marina Ruiz