This is how Comirnaty, the vaccine against covid that is administered in Catalonia, works

BarcelonaEverything is ready for Sunday, when the vaccination against covid-19 will start in Catalonia. Although we will still have to wait to achieve the much desired herd immunity, this is a first step towards controlling the pandemic and reducing mortality. The development of coronavirus vaccines has been an unprecedented challenge and a race to get a vaccine in record time. This has been possible thanks to all the previous research done. This is how Comirnaty works: the name given to the Pfizer vaccine that is starting to be administered in Catalonia on Sunday.

Which vaccine will be administered?

Within the framework of the European strategy of vaccines, agreements have been reached with six pharmaceutical companies for the purchase of vaccines against covid-19 once it has been proved that they are safe and effective. If all the agreements are completed, the EU will have around 2,000 million doses available from various manufacturers, which will be made available as they are approved. Currently, the vaccine from Pfizer and BioNTech is the one that has obtained the authorization from the European Agency of the Medicine (EME) and it is the one that will be administered in Catalonia from December 27th giving priority to the most vulnerable groups of the population.

Who will be vaccinated first?

As the quantity of vaccines will be limited at first - 700,000 doses in the first stage, which goes from January to March, and then will progressively increase -, an order of priority has been established for the population groups to be vaccinated in this first stage:

• Residents and health and social care personnel working in homes for the elderly and for the care of major dependent people.
• Front-line health and social care personnel.
• Other health and social-health personnel.
• Major dependent people (those with degree 3 of dependency) who are not institutionalized.

The first doses of vaccines will be for the first two groups and as more doses become available, the rest will be vaccinated. On the 27th, the first 1595 doses of vaccine will arrive. The vaccination process will start in the Feixa Llarga care home in l'Hospitalet de Llobregat, which has no covid cases. Every Monday the Catalan Government expects that 60,000 doses of the vaccine will arrive and be distributed throughout the country and will be administered by more than 5,000 nursing professionals who have volunteered.

What is the mechanism of action of the vaccine?

The commercial name of the vaccine is Comirnaty, because of the first letters of covid and the messenger RNA molecule (mRNA), which contains the instructions to produce a protein of SARS-CoV-2, the virus that causes covid-19, as explained on the website of the Spanish Agency of Medicines. The Pfizer vaccine does not have the virus itself, and cannot cause the disease.

When a person receives the vaccine, some of their cells will read the mRNA instructions and temporarily produce the protein. The person's immune system will recognize this protein as foreign and produce antibodies and T cells to defend itself. So when you come in contact with the coronavirus, your immune system will recognize it and be prepared to defend itself.

How does the vaccination process work?

The vaccine comes in vials containing several doses that have to be diluted with saline before use. They are kept frozen at -70 degrees and must be thawed before dilution.

Each vial, once diluted, will contain 5 doses of vaccine and each dose is 0.3 ml. Two doses of 0.3 ml will be administered by intramuscular route in the upper arm and with an interval between the first and second dose of at least 21 days.

Are there any contraindications?

While the vaccine is only contraindicated in people who have had a hypersensitivity reaction to a previous dose of a covid-19 vaccine, it is now also recommended that vaccination be postponed for persons with a history of severe allergic reactions.

In the case of people with coagulation disorders, it can be applied with "reasonable safety", as stated in the covid-19 vaccination recommendations document prepared by the Catalan Public Health Agency. In the case of a severe acute illness, vaccination must be postponed, but not in the case of a mild illness without fever.

As there are no studies on pregnancy, vaccination is not recommended for pregnant women either. In the case of women of childbearing age, it is recommended to avoid becoming pregnant in the three months following the injection of the first dose. If a vaccinated woman discovers she is pregnant, the second dose should be stopped and the case should be followed up.

Vaccination should also be postponed for people with suspected covid-19 symptoms and for those in quarantine until they recover. The vaccine can also be given to people who have already had the disease, but for health care workers, priority will be given to vaccinating those who have not yet had it.

What can be the adverse effects?

According to Phase II and III data from clinical trials, the most common adverse effects are: pain at the injection site, fatigue or feeling tired, headache, myalgia, chills, joint pain and fever. Most were of mild or moderate intensity and disappeared after a few days.

When is herd immunity considered to have been achieved?

To achieve herd immunity against coronavirus, 70-80% of the population must be vaccinated. The Government's goal is to close 2021 with more than 12 million vaccines administered.

That is why both health authorities and health professionals remember that with the start of vaccination the pandemic will not have ended - far from it. "The vaccine is important but you have to vaccinate many people for it to be effective", cardiologist Valentí Fuster explained a few days ago at a virtual press conference. Vaccinating 75% of the population "is not a matter of four days, it takes time and people have to be prepared to know that the covid will not disappear in two days", the . That is why Fuster calls for "resilience": "We are not saying that in January this will be over because this will not be the case".

In this sense, Adolfo Garcia-Sastre, director of the Institute of Global Health and Emerging Pathogens at Mount Sinai Hospital, hopes to "return to normality" by "the middle of next year". However, he warns: "The negative part is that we are becoming complacent". "We've been very lucky that this virus can be easily stopped with a vaccine, but we don't know what the next pandemic will look like or if it will be so easy to stop".