You cannot catch COVID from vaccines
No medical intervention is risk-free, but the odds favour getting vaccinated when possible
It is no exaggeration that any medical intervention, including something as benign as taking an Aspirin, carries some risk. This is also true of vaccines. The soldiers in George Washington’s army, during the American Revolution, faced a risk of one per cent mortality when they received their smallpox variolation, a means of creating mild disease, thereby producing immunity. These were better odds than the 30 per cent risk of death for those who caught the disease. Today, any mortality caused by vaccination would be newsworthy.
Vaccines are created in a number of ways. Variolation, as practised in the 18th century, consisted of introducing live virus into the person, with the intention of causing mild disease and creating immunity. The two COVID-19 vaccines approved for use in Canada are MRNA vaccines. No viral material is present. Once within the host cells, the MRNA provides a template for construction of a protein similar to a non-infectious portion of the virus, which prompts the immune system to produce antibodies to that portion of the virus. You cannot catch the disease from the vaccines.
The Pfizer vaccine, (BNT162B2), and the Moderna vaccine, (MRNA-1273), both encode a modification of the spike protein of the coronavirus, which is part of the apparatus needed to bind to human cells. Preliminary data on safety and efficacy from small Phase 1 trials were recently published. Both vaccines produced SARS-COV-2 neutralizing antibody levels similar to those measured in patients who had experienced the disease. Both vaccines were associated with mild to moderate reactions, particularly after the second dose. These consisted of fever, chills, aching muscles, headache, and pain at the injection site.
Phase 3 data from large trials has been published for the Pfizer and Moderna vaccines. The randomized, placebo-controlled trial, of the Pfizer vaccine enrolled 43,448 participants who received an injection of the vaccine, (21,720), or a placebo injection of saline, (21,728). Eight cases of COVID-19 were documented in patients who had received both doses of the vaccine, while 162 cases occurred in those who received placebo injections, consistent with about 95 per cent efficacy for prevention of COVID-19 and before the second dose of vaccine was also documented. Partial protection after the first dose appears to begin around Day 12 following the first dose.
Safety data for a median of two months was available for 37,706 participants of this trial. Only one case of severe COVID-19 occurred in a vaccine recipient and adverse events similar to those in the preliminary trials were identified. No deaths attributable to the vaccine were reported.
Data for the Moderna vaccine, (MRNA-1273), has also published. Using a similar MRNA platform, the Moderna vaccine demonstrated 94.1 per cent efficacy, nearly identical to that of the Pfizer vaccine, in a randomized, placebocontrolled trial of 30,420 participants in the U.S. All cases of severe COVID-19, (30), occurred in the placebo group. Adverse reactions were similar to those in the Pfizer trial, and no serious safety concerns were identified.
To bring a vaccine forward for regulatory approval ordinarily takes a decade. First doses of both vaccines were given in July, 2020. Vaccines are costly to produce and do not generate a great deal of income for pharmaceutical companies. Creating vaccines in such a short time-frame has been a remarkable achievement. Vaccine platforms for the SARS-COVID-1 pandemic of 2002-3 were developed but the disease itself disappeared spontaneously and efforts to create a coronavirus vaccine were discontinued. It is not expected that SARS COVID-19 will disappear any time soon.
Concerns regarding long-term safety and the length of immunity provided remain and have been acknowledged. “Vaccine hesitancy” (related to measles vaccination), has been listed among the top 10 threats to global health by the WHO. Over the next few months, individuals will have to make personal decisions regarding their willingness to receive these vaccines. It should be remembered by those who worry about the longterm consequences of vaccination, that known short-term risks of mortality are becoming more clearly defined as the pandemic progresses. Long-term effects of COVID-19 are also being discovered, some of which seem to be permanent. These are in addition to the known risks of stroke and other complications of the acute disease.
Messenger RNA vaccines are free of viral material and cannot cause infection with COVID-19. No health care intervention is 100 per cent safe. However, the state of our knowledge about COVID-19 at present weighs heavily in favour of accepting vaccination as a means of personal protection and provision of widespread immunity. Both will be required before we can go back to our normal lives.