Achim Regenauer, Chief Medical Officer PartnerRe, shares his personal view of the issues relating to a SARS-CoV-2 vaccine’s future efficacy, but with a positive end note.
To date, no vaccine has ever been developed against coronaviruses; there is no vaccine, for example, for SARS (severe acute respiratory syndrome) or for the four long-standing coronaviruses that have been in circulation for years causing common colds. We must still recover from all these viruses without a vaccine. That said, the prognosis for a SARS-CoV-2 vaccine is good given the immense worldwide efforts now well underway1.
But there are several issues to be aware of:
Many patients with an asymptomatic or mild form of COVID-19 have experienced falling antibody levels (by as much as 23-fold) in the three months following COVID-19 diagnosis2. This could mean (at least in part) that immunity is not permanent. Immunity proffered by a vaccine is likely to function in the same way, meaning that vaccination will need to be repeated.
It remains unknown if a vaccine would give full immunity against SARS-CoV-2, or only protect against more severe forms of the disease. It’s therefore possible that transmission of the virus would not be stopped by vaccination.
Mutations are part of the natural evolution process as a virus tries to escape from immune system defences (human antibodies). Fortunately, unlike influenza viruses, SARS-CoV-2 has a slow mutation rate3, but the more a virus circulates worldwide, the greater the likelihood that a new variant will emerge. The receptor-binding domain (RBD) of the human spike protein enables the virus to enter human cells and is the main target of a new vaccine. If mutations emerged at the sensitive RDB location it could render a vaccine ineffective.
However, on a positive note, history has shown us that viruses tend to mutate and evolve over several years to become less pathogenic, whilst hosts become more resistant4,5.
Therefore, even if a fully effective vaccine remains elusive, SARS-CoV-2 will eventually become another coronavirus that causes runny noses, common colds and, in a minority of cases, pneumonia.
Achim Regenauer, Chief Medical Officer, Europe and Asia Pacific
1How close are we to a coronavirus vaccine? PartnerRe (2020)
2Jeffrey Seow et al., Preprint: Longitudinal evaluation and decline of antibody responses in SARS-CoV-2 infection. https://www.medrxiv.org/content/10.1101/2020.07.09.20148429v1.full.pdf
3Tarek Alouane et al. Preprint: Genomic diversity and hotspot mutations in 30,983 SARS-CoV-2 genomes https://www.biorxiv.org/content/10.1101/2020.06.20.163188v1.full.pdf
4Markham Heid; Could the Coronavirus Be Weakening as It Spreads? https://elemental.medium.com/could-the-coronavirus-be-weakening-as-it-spreads-928f2ad33f89
5Parrish, C.R. et al., Cross-Species Virus Transmission and the Emergence of New Epidemic Diseases, doi: 10.1128/MMBR.00004-08 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2546865/