Q&A with Dr. David Bar-Or on the COVID-19 Vaccines and the Variants

Does the vaccine change your DNA? Does the virus or infection change DNA?

The vaccine is composed of mRNA encapsulated with lipid particles so that it can enter the cell. The lipid layer merges with the cell membrane while the mRNA enters the cytoplasm. This mRNA encodes for the spike protein of SARS-CoV2, so it uses the cell machinery to produce the viral spike protein, which in turn exits the cell and becomes exposed to our innate and adaptive immune system. The immune system then produces neutralizing antibodies to the spike protein, priming the immune system to fight potential viral exposure. The mRNA in the vaccine consists of modified nucleic acids and is unable to replicate, unlike the virus. The mRNA in the vaccine does not get into the cell nucleus where the DNA resides and therefore does not affect or change our DNA.

The virus, however, does affect our DNA by incorporating itself, through complex mechanisms, into our DNA and code the cell to make viral RNA and virions. The viral RNA is therefore able to replicate itself by utilizing our DNA and cell machinery.

Our immune system learns by exposure. In the case of a vaccine, once the mRNA goes into the cell, what occurs?

The mechanism of formation of the spike protein and its presentation to B cells and T cells in the adaptive immune system results in formation of antibodies to the SARS-CoV2 spike protein, which is the main protein responsible for the virus’ ability to attach to and invade our cells. After the exposure, memory B and T cell stay in our system for some time (research has yet to determine for how long), and antibodies remain for several months (again, the research is unclear on how long), ready to act in case of exposure to the virus.

Infection refers to getting the virus but disease refers to developing symptoms from the virus. Do the Pfizer or Moderna vaccines prevent you from getting COVID-19?

Signs and symptoms of viral infections are the result of both the virus itself causing tissue destruction and the host immune response. The vaccine has not been demonstrated to prevent the spread of the virus or reduce the likelihood that someone is infectious. It may prevent us from having a severe disease.

It is not clear if the vaccine elicits formation of different kinds of antibodies – like IgE or IgA – in addition to IgG. IgG is the main antibody in circulation and was the one that was measured in the trials, but IgA is the main antibody defense in mucosal surfaces. Theoretically, one could be immune systemically but still have viruses on the mucosal surfaces, like the upper respiratory airway, and could be infectious to others. Research is ongoing on this question.

Do the Pfizer vaccines address both the virus (infection) and the disease?

Yes , if you eliminate the virus/viral load, then the disease will be either asymptomatic or very mild. In the clinical trials for both Pfizer and Moderna, efficacy was determined by occurrence of symptomatic patients. We do not have data on how many asymptomatic ones there were in these studies.

Does the vaccine prevent the spread of COVID-19?

No. The vaccine has not been demonstrated to prevent the spread of the virus or reduce the likelihood that someone is infectious. It may prevent us from having a severe disease.

If I get vaccinated, do I still need a mask? Do I still need to social distance?

Yes, until herd immunity is achieved (at least 70 to 80% of the population vaccinated or recovered from COVID-19), these measures should continue. The vaccine does not prevent the spread of the virus.

Should we worry about the new variant reported in the UK and other countries?

The good news is that the World Health Organization (WHO) reported that the current vaccine is probably effective against this variant. The variant was reported to have at least 22 mutations, and most of these mutations are not important for the receptor binding domain of the spike protein. However, if the virus is not eradicated by massive vaccination of the world population, because it mutates so rapidly (though more slowly than the flu virus), a new variant could become resistant to the current vaccine. This newly discovered variant is 40 to 70% more infectious than the previous one and accounts for over 70% of new cases in the U.K. It is unknown if it is more virulent.

mRNA vaccines have the advantage that they can be modified in the lab and manufacturing scaled up very rapidly, so the vaccines can be adapted to new variants if necessary.