Preguntas frecuentes sobre la vacuna Moderna

Reading time: 4 min
Does the Moderna vaccine have a trade name?

Not at the moment. Technically, it is called mRNA-1273. 

What is its goal?

It is a vaccine for preventing coronavirus disease (COVID-19) in people over 18 years of age. The vaccine does not contain SARS-CoV-2 and cannot cause COVID-19. 

How does the Moderna vaccine work?

The vaccine contains a molecule called mRNA (messenger RNA) that includes the instructions for producing the S (spike) protein of the virus (the one the virus needs to be able to enter human cells). 

When a person receives the vaccine, some of their cells read the mRNA instructions and temporarily produce the S-protein. Their immune system recognises this protein as being foreign, so it produces antibodies, and activates T-cells (lymphocytes) to attack it. If that person then comes into contact with the SARS-CoV-2 virus, their immune system quickly recognises it and initiates a defence response against the virus. 

The vaccine requires two doses at least 28 days apart. 

What happens to the mRNA afterwards?

The mRNA in the vaccine does not stay in our bodies. It is destroyed just a few hours after the vaccination. It never comes into contact with the cell nucleus (the whole process takes place in the cytoplasm) and there is therefore no risk of any genetic modification. 

How effective is this vaccine?

A clinical trial has been conducted on over 30,000 participants. Half of them received the vaccine (vaccinated group) and half were given a placebo (control group). 

The vaccine's effectiveness was determined in more than 28,000 participants aged over 18 who showed no signs of previous infection. The study showed a 94% reduction in the number of symptomatic cases of COVID-19 in the vaccinated group (11 cases out of 14,134 vaccinated) when compared to the control group (185 cases out of 14,073 unvaccinated). The vaccine was also 91% effective among participants with risk factors for severe disease caused by COVID-19 (asthma, COPD, diabetes, arterial hypertension, and obesity). 

When do you become immune?

14 days after the first dose there is already immunity. This reaches peak protection after the second dose. 

Can people who have already had COVID-19 be vaccinated with the Moderna vaccine?

In the clinical trial, 343 individuals who had already had COVID-19 were vaccinated. These people were excluded from the effectiveness analysis, however, no particular or special side effects were recorded among these participants. 

There is not enough data to conclude how the vaccine works in people who have already had COVID-19. The current guidelines recommend waiting at least three months from the disease recovery date before vaccinating these people. 

Can the vaccine reduce person-to-person transmission of the virus?

We still do not know. It is not known what percentage of people who have been vaccinated may still carry the coronavirus and transmit the infection. 

How long does the vaccine’s protection last?

We still do not know. All the trial participants will continue to be monitored (for up to 2 years) to provide further information on how long the protection lasts. Experimental data indicates that immunity to COVID-19 is likely to last for months or years, but not for life. 

Why can't children under 18 be given this vaccine?

The Moderna vaccine is not recommended for children under 18 years of age because there is currently no information about the effects on this age group. The EMA has reached an agreement with Moderna to conduct a trial on this population group at a later stage. 

Can immunosuppressed people be given this vaccine?

The data is still limited. It is possible that immunosuppressed people will not respond as well to the vaccine, but from a safety perspective there are no additional problems. Immunosuppressed people can be vaccinated, as their risk of developing severe forms of COVID-19 is high. 

Why can't pregnant women be given this vaccine?

Based on the information available to date and accumulated experience, the vaccination of pregnant women is safe. It is also recommended, as SARS-CoV-2 infection during pregnancy increases the risk of complications and the development of severe COVID. It can be administered at any time during pregnancy, and women planning a pregnancy can receive any of the COVID vaccines without having to wait between vaccination and conception.

Breastfeeding women can receive the vaccine without having to stop breastfeeding.  Moreover, an added benefit of vaccinating pregnant and breastfeeding mothers is that the antibodies generated are transferred to the foetus through the breast milk.

According to the Spanish Ministry of Health, the Pfizer/BioNTech and Moderna vaccines are recommended during pregnancy and breastfeeding, but other vaccines may be used in other countries.

What side effects may occur with this vaccine?

Most people who are vaccinated will not experience significant side effects. These may appear during the first week after vaccination. They are not usual after the first two days. The frequent mild or moderate effects observed in clinical trials were (source EMA): 

In more than 1 out of 10 people vaccinated: 

  • Pain and swelling at the injection site. 

  • Tiredness. 

  • Headache

  • Muscle pain (myalgia) and/or joint pain (arthralgia). 

  • Fever

  • Nausea and vomiting. 

  • Swelling of the ganglia (adenopathy) in the armpit. 

In less than 1 out of 10 people vaccinated: 

  • Redness. 

In less than 1 out of 100 people vaccinated: 

  • Itching at the injection site. 

In less than 1 out of 1,000 people vaccinated: 

  • Swelling of the face. This may affect people who have received cosmetic injections in the past. 

  • Transient weakness of the facial muscles (acute peripheral facial paralysis). 

Painkillers, like paracetamol, can be taken if necessary to mitigate these effects. 

Substantiated information by:

Antoni Trilla
Eduard Vieta Pascual
Gema Maria Lledó Ibáñez
Jacobo Sellarés Torres
Josep M. Miró Meda
Josep Maria Peri
Maica Rubinat
Mariona Violan

Published: 12 March 2020
Updated: 12 March 2020

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