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The Moderna COVID-19 (mRNA-1273) vaccine: what you need to know

22 February 2022

Updated 23 February 2022, pursuant to updated interim recommendations.

The WHO Strategic Advisory Group of Experts on Immunization (SAGE) has issued updated interim recommendations for the use of the Moderna COVID-19 (mRNA-1273) vaccine against COVID-19. This article provides a summary of those interim recommendations; you may access the full guidance document here.

Here is what you need to know.

Who should be vaccinated first?

As with all COVID-19 vaccines, health workers at high risk of exposure and older people should be prioritized for vaccination.

As more vaccine becomes available, additional priority groups should be vaccinated, with attention to people disproportionately affected by COVID-19 or who face health inequities.

Who else can take the vaccine?

The comorbidities studied in in the phase 3 clinical trial included chronic lung disease, significant cardiac disease, severe obesity, diabetes, liver disease and human immunodeficiency virus (HIV) infection. Vaccination is recommended for persons with such comorbidities that have been identified as increasing the risk of severe COVID-19.

Immunocompromised persons are at higher risk of severe COVID-19 disease, including persons living with HIV. As the immune response is reduced in such persons, an additional dose (third dose) is recommended as part of the primary vaccine series, 1-3 months after the second dose. Known HIV positive vaccine recipients should be provided with information and counselling.

Vaccination can be offered to people who have had COVID-19 in the past. But individuals may wish to defer their own COVID-19 vaccination for up to six months from the time of SARS-CoV-2 infection.

Vaccine effectiveness is expected to be similar in breastfeeding women as in other adults. WHO recommends the use of the vaccine in breastfeeding women as in other adults. WHO does not recommend discontinuing breastfeeding because of vaccination.

Should pregnant women be vaccinated?

Given the adverse consequences of COVID-19 during pregnancy and the increasing data supporting a favorable safety profile of mRNA-1273 in pregnancy, WHO recommends the use of mRNA-1273 in pregnant individuals. WHO does not recommend pregnancy testing prior to vaccination. WHO does not recommend delaying pregnancy or terminating pregnancy because of vaccination.

Who should not take the vaccine?

Individuals with a history of severe allergic reaction to any component of the vaccine should not take this or any other mRNA vaccine.

Individuals who developed myocarditis or pericarditis following the first dose of mRNA-1273 vaccine should not receive additional doses of any COVID vaccine unless with the recommendation of their doctor or a healthcare professional. 

The vaccine should not be administered to persons younger than 12 years of age pending the results of further studies.

Can children and adolescents take the vaccine?

A phase 3 trial of the Moderna vaccine in adolescents aged 12–17 years showed that the vaccine was well tolerated, immunogenic, and efficacious.

WHO recommends the vaccine is taken in 2 doses (100 µg, 0.5 ml each) given intramuscularly, 8 weeks apart.

WHO recommends that countries should consider using the vaccine in children aged 12-17 only when high vaccine coverage with 2 doses has been achieved in the high priority groups as identified in the WHO Prioritization Roadmap. 

Children and adolescents aged 12-17 years of age with comorbidities that put them at significantly higher risk of serious COVID-19 disease, should be offered vaccination, alongside other high-risk groups.

Studies on the safety and efficacy of the vaccine in children aged below 12 are still ongoing.

What’s the recommended dosage?

SAGE recommends the use of the Moderna mRNA-1273 vaccine at a schedule of two doses (100 µg, 0.5 ml each) 8 weeks apart. 

Compliance with the full schedule is recommended and the same product can be used for both doses.

SAGE recommends that severe and moderately immunocompromised persons should be offered an additional dose of vaccine. This is due to the fact that this group is less likely to respond adequately to vaccination following a standard primary vaccination series and are at higher risk of severe COVID-19 disease. 

Is a booster dose recommended for this vaccine?

A booster dose may be considered 4 – 6 months after completion of the primary vaccination series, though this is mainly recommended for the higher priority-use groups, in accordance with the WHO Prioritization Roadmap.

WHO recommends the dosage of the booster dose is half the dose used in the primary vaccination series (50 µg at 0.25 ml).

The benefits of booster vaccination are recognized following increasing evidence of waning vaccine effectiveness against mild and asymptomatic SARS-CoV-2 infection over time. 

Can this vaccine be ‘mixed and matched’ with other vaccines?

SAGE accepts two heterologous doses of WHO EUL COVID-19 vaccines as a complete primary series.

For countries considering heterologous schedules, WHO has made recommendations to ensure equivalent or favourable immunogenicity or vaccine effectiveness for heterologous versus homologous schedules:

  • Either of the WHO EUL COVID-19 vectored vaccine (Janssen or AstraZeneca Vaxzervia/COVISHIELD) can be used as a second dose following a first dose of the Moderna vaccine, dependant on product availability.
  • The Moderna vaccine can also be used as a second dose following any of the WHO EUL COVID-19 inactivated vaccines (Sinopharm, Sinovac or Bharat) or any of the vectored vaccines (Janssen or AstraZeneca Vaxzervia/COVISHIELD) 

Is it safe?

On 30 April, WHO listed the Moderna vaccine for emergency use. WHO’s Emergency Use Listing (EUL) assesses the quality, safety and efficacy of COVID-19 vaccines and is a prerequisite for COVAX Facility vaccine supply.

The EMA has thoroughly assessed the data on the quality, safety and efficacy of the Moderna COVID-19 vaccine and authorized its use across the European Union.

SAGE recommends that all vaccinees be observed for at least 15 minutes after vaccination. Those who experience an immediate severe allergic reaction to the first dose should not receive additional doses.

Longer-term safety assessment involves continued follow up of clinical trial participants, as well as specific studies and continued surveillance of secondary effects or adverse events of those being vaccinated in the roll out.

The Global Advisory Committee on Vaccine Safety, a group of experts that provides independent and authoritative guidance to the WHO on the topic of safe vaccine use, receives and assesses reports of suspected safety events of potentially international impact. In October 2021, the GACVS COVID-19 subcommittee concluded that the mRNA COVID-19 vaccines have clear benefits in all age groups in reducing hospitalizations and deaths due to COVID-19.

How does this vaccine compare to other COVID-19 vaccines already in use?

It is impossible to compare vaccines head-to-head due to the different approaches taken in designing the respective studies, but overall, all of the vaccines that have achieved WHO Emergency Use Listing are highly effective in preventing severe disease and hospitalization due to COVID-19.

How efficacious is the vaccine?

The Moderna vaccine has been shown to have an efficacy of approximately 94.1 per cent in protecting against COVID-19, starting 14 days after the first dose, in the context of the ancestral strain.

Does it work against new variants?

Vaccine effectiveness against new variants of concern such as Delta and Omicron is relatively well maintained against severe disease, but lower against breakthrough infections. 

Does it prevent infection and transmission?

There is only modest impact on preventing mild infections and transmission, particularly in the context of Omicron. 

Immunity persists for several months, but the full duration is not yet known. A booster dose restores vaccine effectiveness against Omicron, in particular against severe disease.

In the meantime, we must maintain public health measures that work: masking, physical distancing, handwashing, respiratory and cough hygiene, avoiding crowds, and ensuring good ventilation.

This webpage was updated on 23 February 2022 to update the latest guidance.

This webpage was updated on 5 January 2022 to update the latest guidance and ensure consistency of information and formatting.

This article was revised on 29 January 2021 to include a section dedicated to pregnant women, but the recommendations remain the same.