Within a year from the discovery of the SARS-CoV-2 virus that causes COVID-19 two vaccines had already received conditional marketing authorization from the European Medicines Agency, after completing phase III trials showing safety and efficacy in 30-40 thousand individuals.

Today 15 vaccines are being offered to the general population in different countries and another 26 are in phase III trials and around 200 in early clinical or preclinical phases. Phase III  trials and mass vaccination has shown that the vaccines are highly efficaceous in preventing disease and severe outcome, whereas less is known about their effectiveness against infection and transmission. The licenced vaccines are of different types; mRNA, viral vectors,  proteins or whole inactivated viruses, which have different advantages and disadvantages. We do not know how long protective immunity lasts, if or when a booster vaccination is necessary.  

A major challenge is the unequal and unfair distribution of vaccines globally, which deprives many people, mainly in low and middle income countries, of their rights to receive vaccination as a preventive health care. It also contributes to generation of new viral strains, that through mutation may become more infectious, more pathogenic and escaping the immune response generated by infection or vaccination based on the original SARS-CoV-2 viral strain.

Another major challenge is rapid generation of „variant“ based vaccines that prevent better against the emerging SARS-CoV-2 variants, in particular the „escape“ variants, in large enough quantities to vaccinate large parts of the world’s population. Herd immunity is important to protect those that cannot be vaccinated and to stop the pandemic.  Lack of supply and inequitable distribution of vaccines remains the biggest threat to ending the pandemic and driving a global recovery.