With more people receiving their COVID-19 vaccinations every day, there’s reason to be optimistic about the virus getting under control and case rates coming down.
However, the new Delta variant is a variant of concern. According to Public Health England, the Delta variant is more easily transmitted and could cause an increased risk of hospitalization in comparison to the Alpha strain.
Why It is Important to Get Your Second COVID-19 Vaccine Dose?
Studies from the UK and Israel showed about 65% effectiveness with one dose of the Pfizer vaccine. A later study from the CDC showed 90% effectiveness with two doses of Pfizer vaccine.
With such high rates of effectiveness, getting both doses better protects you against not just getting COVID-19, but from serious illness, hospitalization, and even death as a result of getting sick. Booster shots, in general, allow our immune system to retain memory or knowledge of a virus for a longer period of time.
What If I received the Oxford-AstraZeneca (in Canada) Vaccine First? What Should I Do for My Second Dose?
On June 17, the Canadian National Advisory Committee on Immunization (NACI) said people who got the Oxford-AstraZeneca vaccine as their first dose should get Pfizer-BioNTech or Moderna for their second shot.
NACI now recommends that an mRNA vaccine is preferred as both a first dose and second dose unless an mRNA vaccine is inaccessible or there is a contraindication, for example, an allergy to an mRNA vaccine or its components.
In making its recommendations, NACI considered:
- The increasing availability of mRNA vaccines (Pfizer-BioNTech, Moderna) in Canada.
- Emerging evidence suggesting better immune responses when a first dose of the AstraZeneca vaccine is followed by a second dose of the Pfizer-BioNTech mRNA vaccine.
- The risk of Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) associated with viral vector vaccines (AstraZeneca, Janssen) but not associated with mRNA vaccines (Pfizer-BioNTech, Moderna).
Can I Mix Pfizer and Moderna Vaccines as the Second Dose Due to the Shortage of First Dose Brand?
According to Canada’s new guidance, people who received a dose of mRNA vaccine should be given the same vaccine if it is readily available, but an alternative brand of mRNA vaccine, namely those from Pfizer and Moderna, can be offered. So that means they are considered interchangeable.
The website of the U.S CDC is indicating that in exceptional situations in which the mRNA vaccine product given for the first dose cannot be determined or is no longer available, any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses to complete the mRNA COVID-19 vaccination series. Despite this statement, the CDC indicates “every effort should be made to ensure completion of the vaccine series with the same product.”
How Effective are the COVID Vaccines Against the Delta Variant?
According to figures gathered by Public Health Scotland and published in the Lancet, at least two weeks after the second dose of Covid vaccine jabs, protection against infection fell from 92% for the Alpha variant to 79% against the Delta variant for the Pfizer/BioNTech vaccine, while for the Oxford/AstraZeneca vaccine the protection fell from 73% to 60% respectively.
Which mRNA Vaccine Is Better, Pfizer or Moderna?
Both Pfizer and Moderna’s vaccines have proved remarkably effective.
In clinical trials, Moderna showed 94.1 percent efficacy in preventing COVID-19 two weeks after a second dose, comparable to Pfizer’s 95 percent. Both trials saw zero hospitalizations and deaths in those who did get COVID-19 after being vaccinated — key metrics.
Side effects from each of the mRNA vaccines have also been similar, with neither producing more adverse events than the other.
In the end, the best COVID-19 vaccine is the first one that is available to you. In Canada, the recommendation is don’t wait for a specific brand. All currently authorized and recommended COVID-19 vaccines are safe, effective, and reduce your risk of severe illness. Pharmacists are ideally positioned to have a discussion about the recommendations and what your options are.
A note on the Johnson & Johnson / Janssen Vaccine
The WHO has indicated that a comparison of vaccines head-to-head cannot be done due to the differences in the study design. According to the WHO, a single dose of the J&J will provide 85.4% efficacy against severe disease and hospitalization. As of this writing, the author was unable to find an efficacy rate against the Delta variant of concern with the J&J.
Pharmacies are ideally positioned to have a discussion about the recommendations and what your options are. Speak to your pharmacist if you have any questions about which vaccine is best for you.
- cdc.gov (https://www.cdc.gov/mmwr/volumes/70/wr/mm7013e3.htm )
- abc.net.au (https://www.abc.net.au/news/health/2021-06-09/covid-19-vaccines-mix-match-pfizer-astrazeneca-australia/100188824)
- Canada.ca (https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines/summary-statement-june-17-2021.html?hq_e=el&hq_m=2186351&hq_l=2&hq_v=8f36db19ae )
- Healthline.com (https://www.healthline.com/health-news/why-its-crucial-to-get-your-second-dose-of-covid-19-vaccine )
- businessinsider.com (https://www.businessinsider.com/coronavirus-vaccine-mixing-doses-canada-says-interchangeable-cdc-against-2021-6 )
- World Health Organization: https://www.who.int/news-room/feature-stories/detail/the-j-j-covid-19-vaccine-what-you-need-to-know