Covid-19 vaccines: Where do we stand one year later?

Since the beginning of the pandemic, researchers and laboratories around the world have mobilised to develop effective vaccines against COVID-19.

The first vaccine against SARS-CoV-2 to be authorised by the European Medicines Agency (EMA) was that of Pfizer/BioNTech, on 21 December 2020.

To date, five COVID-19 vaccines have received Marketing Authorisation (MAc) in Europe and four of them are currently available in France:

  • Comirnaty from Pfizer/BioNTech (mRNA vaccine)
  • Spikevax from Moderna Biotech (mRNA vaccine)
  • AstraZeneca's Vaxzevria (viral vector vaccine)
  • Johnson & Johnson's Covid-19 Janssen (viral vector vaccine)

Since its launch at the end of 2020, the vaccination campaign against COVID-19 has made it possible to contain the impact of the epidemic and reduce mortality and morbidity linked to the viral infection.

The efficacy of vaccines against severe forms of COVID-19 is around 90%.

The majority of adverse events are expected and not serious.

The surveillance set up shows that :

  • the majority of reported adverse events are not serious and were observed during clinical trials
  • the new adverse events identified do not question the safety of the vaccines

How does an mRNA vaccine work?

Messenger RNA vaccines involve injecting laboratory-made mRNA molecules into the body. This mRNA will enter our cells, but not their nucleus, and instruct them to make the S protein that is specific to the virus responsible for COVID-19. This will activate the immune response. The mRNA is then quickly eliminated, so it does not change our DNA.

How does a viral vector vaccine work?

Viral vector vaccines involve using a virus that is harmless to humans (in this case an adenovirus) into whose genome some of the genetic material from SARS-CoV-2 (the protein S gene) has been introduced. When the adenovirus enters our cells, it gives instructions to make the SARS-CoV-2 S-protein. This S protein will be recognised as foreign to the body and trigger the immune response.

Nevertheless, the need for vaccines against SARS-CoV-19 remains very high as the virus continues to spread and new variants emerge worldwide. The omicron variant is now predominant in France.

The fifth COVID-19 vaccine has just arrived in Europe. It is the Nuvaxovid vaccine from Novavax (marketing authorisation date is 20 December 2021). It is a recombinant protein vaccine. The principle consists of producing the S protein of wild SARS-CoV-2 (Wuhan strain) in culture and then delivering it to the body with an adjuvant in order to stimulate immunity and trigger the production of antibodies.

Nuvaxovid was given the green light by the French National Authority for Health (HAS) on 14 January 2022.

To be continued...