Why would one ever consider mixing vaccines?

Both Moderna’s and Pfizer’s vaccines were evaluated to be around 95% effective. Each is meant to be a two-dose vaccine. One dose is given and a designated time later the second dose is given.

The United Kingdom has approved AstraZeneca’s vaccine which is reported to be around 90% effective. AstraZeneca has not been approved in the United States for its vaccine. Emergency Use Authorization is being talked about for April for AstraZeneca.

England’s Option

https://www.newsmax.com/scitech/britain-moderna-pfizer-vaccinations/2021/01/02/id/1003974/ The United Kingdom decided to allow mixing vaccines. Mixing, in this context, means that a person who received the Pfizer vaccine first may opt to get the Moderna second dose or the AstraZeneca dose. This is a rare option and available to a select few.

Availability of a vaccine at a location can be interrupted for a variety of reasons. Rather than have a high-risk patient wait longer than thought prudent, the Public Health of England has authorized mixing vaccines to complete the vaccination process.

Abandoning Science?

https://www.independent.co.uk/news/uk/home-news/covid-vaccine-uk-mixing-b1781707.html Just when one article (New York Times https://www.nytimes.com/2021/01/01/health/coronavirus-vaccines-britain.html) appears and states that the Public Health England has refuted that statement (British Medical Journal https://www.bbc.com/news/uk-55519042). The fine print says that it is not recommended but can be allowed in exceptional cases.

Both Pfizer and Moderna use an mRNA vaccine. AstraZeneca’s vaccine is not an mRNA variant. However, both Pfizer and AstraZeneca base their vaccines on the coronavirus spike protein structure and alignment. Not stated explicitly in the earlier article is that one would assume that an mRNA vaccine would be followed up by a similar type of vaccine.

Not so in England. A few people think that more protection might be offered by having the initial inoculation with Pfizer and the second with AstraZeneca. The confusion reigns because some authorities do not want to mix an mRNA vaccine with a non-mRNA vaccine.

Who is really in charge? Are authorities so scared that they are abandoning science and clinical trials to offer a second vaccine on time?

Who is Right?

https://www.theguardian.com/world/2021/jan/02/england-health-officials-defend-contingency-plan-to-mix-covid-vaccines The Joint Committee on Vaccination and Immunisation declared that studies are ongoing currently to evaluate mixing strategies of two different COVID-19 vaccines. It would be a contingency plan only in extreme situations.


This sounds like a conversation a couple of scientists were having about a worst-case scenario of vaccine availability and mixing two different vaccines was brought up. I cannot imagine that this is being discussed in the newspapers and other media.

The CDC and FDA have strict guidelines for clinical trials. In the heat of the battle, not even a month old, a new plan is being hatched to cover a contingency that may or may not exist for very few people.

Pfizer’s report (https://www.bmj.com/content/371/bmj.m4826) shows the efficacy of the first dose only of their vaccine at 52%. Both doses provide 95% effectiveness. What about not mixing vaccines and only delaying the second dose until manufacturing is caught up with the distribution. That theory was thrown out by the chair of the department of medicine at the University of California at San Francisco and the dean of the Brown University School of Public Health (https://www.washingtonpost.com/opinions/2021/01/03/its-time-consider-delaying-second-dose-coronavirus-vaccine/).

Are we already off the rails on vaccine delivery? A logistics plan should have firm metrics of who is getting vaccines first if you get 20% of the delivery of 60% of the delivery. Back-up plans should exist to account for prioritizing the second vaccine to those who had already received the first. This cannot be that difficult. Are officials that paranoid?

From a military and logistics background, I find it hard to believe that this has not been worked out months ago before the vaccines were approved and manufactured.

Live Longer & Enjoy Life! – Red O’Laughlin – RedOLaughin.com


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