Experimental vaccine Generates Antibody Levels Up to Three Times Those Of Recovered COVID-19 Patients

An experimental Covid-19 vaccine being developed in Oxford by Pfizer and BioNTech could provide protection lasting several years, but also caused fever and other side effects in a high proportion of recipients.

The preprint study randomly assigned 45 patients to get either a placebo or one of three doses of the vaccine, followed by a booster injection three weeks later. However, the highest dose was not given a second time because it caused fevers in half of the recipients.

The vaccine is based on messenger RNA (mRNA), a molecule which carries genetic information from the DNA to the cell’s protein building machinery. The vaccine introduces mRNA that encodes the Sars-CoV-19 spike protein, which is then produced by cells and recognised by the immune system, resulting in antibody generation. This video from 2017 by moderna, who are also developing an mRNA vaccine against COVID-19, discusses the advantages of this approach, particularly when it comes to pandemics:

In the trial, the vaccine did indeed result in the generation of antibodies against the virus, some of which were neutralising (preventing the virus from functioning). Levels of neutralizing antibodies were 1.8 to 2.8 times the level measured in recovered Covid patients.

The lower dose booster injections produced higher antibody levels than the single higher dose. However, over 50% of participants receiving one of the two lower doses still reported some form of adverse effect following the second injection, though none of these were serious.

It is still uncertain whether the higher levels of antibodies will confer immunity. Confirming this will require larger trials in populations in which the virus is circulating. Such studies are expected to begin primarily in the USA this summer.