Mix & Matching COVID Vaccines

5 min readFeb 5, 2021

Professor Matthew Snape, Oxford’s chief investigator on the trial, said: “This is a tremendously exciting study that will provide information vital to the roll out of vaccines in the U.K. and globally… If we do show that these vaccines can be used interchangeably in the same schedule this will greatly increase the flexibility of vaccine delivery, and could provide clues as to how to increase the breadth of protection against new virus strains.”

NB: Definitely not done yet, here are my sources and WHY I’m looking into this niche vaccine topic.

Britian to Mix & Match vaccines (waiting for the dataset), will be sharing findings (if dataset is ever released) with The COVID-19 Tracking Project by The Atlantic.
For more information on COVID-19 vaccines, please visit: https://www.cdc.gov/vaccines/covid-19/index.html

What am I doing exactly?

I’m currently working on the range of mixing and matching COVID vaccines. For example, I get Pfizer's then I get Moderna's for my second dose. In particular, this will focus on the mRNA variant of the vaccine. What are the dangers? If any dangers at all. Once I receive/look at the UK dataset, I can continue finishing the Python script that can estimate efficacy.

Why am I focusing on such a niche limited scope of the vaccine rollout of 2021?

I find this particular quagmire in the vaccine efforts fascinating, on one hand if you can mix and match, it would speed up the vaccination rollout possibly two folds, on the other, we know if we use Pfizer + Pfizer, there’s an extremely high success rate. What do we know about mixing Pfizer and Moderna? Let’s say we start off with a Pfizer shot, then 28 days later a Pfizer shot isn’t readily available but a Moderna shot is? Do we know, once the mix variant of the vaccine is deployed, would it cause anaphylaxis or something else?

Once I get the UK data

In theory, once I get the UK data, with the current code I have (that hasn’t been pushed), it looks a bit like this:

covid_vacc_pfizer_first_dose_date=patients.with_tpp_vaccination_record(
product_name_matches="COVID-19 mRNA Vac BNT162b2 30mcg/0.3ml conc for susp for inj multidose vials (Pfizer-BioNTech)" # Can add Moderna, AstraZeneca for Mix n Match

Current list I’m using:

"Pfizer (Final)" : {"n_p":262, "n_v":8, "v2p_ratio":1.0, "xlo":0.75},
"Pfizer (Severe)" : {"n_p": 9, "n_v": 1, "v2p_ratio":1.0, "xlo":0.0},
"Moderna (Interim)" : {"n_p":90, "n_v":5, "v2p_ratio":1.0, "xlo":0.70},
"Moderna (Final)" : {"n_p":185, "n_v":11, "v2p_ratio":1.0, "xlo":0.75},
"Moderna (Severe)" : {"n_p": 30, "n_v":0, "v2p_ratio":1.0, "xlo":0.70},
"Sputnik V (Interim)" : {"n_p":31, "n_v":8, "v2p_ratio":3.0, "xlo":0.45},
"AstraZeneca SD+SD" : {"n_p":71, "n_v":27, "v2p_ratio":1.0, "xlo": 0.3},
"AstraZeneca LD+SD" : {"n_p":30, "n_v":3, "v2p_ratio":1.0, "xlo":0.3},
"CoronaVac (Interim, Turkey)" : {"n_p":26, "n_v":3, "v2p_ratio":752.0/570.0, "xlo":0.3},

What would happen if only Moderna doses are available? Are they interchangeable? Is it safe to switch? (Question from Bloomberg)

“This is a great question, and one that many other newsletter readers raised this past week. The Moderna and Pfizer vaccines are remarkably similar. Each uses a technology called messenger RNA (mRNA) to teach cells how to make a protein that will trigger an immune response to the virus, preparing the body for a potential encounter with it in the wild.” — Ramon Lorenzo Redondo, PhD.

Describing the situation with Python

I’ve wrote a Python script that describes the issue at hand, if maybe this is all too much information and you just want to get to the point.

is_pfizer = False  
is_moderna = Trueif is_pfizer and is_pfizer:
    print("it works!") # If pfizer is pfizer, then OK 
if is_pfizer and is_moderna:
    print("we are not sure!") # If pfizer then moderna, then NOT SURE

The script states the obvious, if it’s Pfizer + Pfizer = OK. If it's Pfizer + Moderna = NOT SURE.

Quotes from an expert

“The Pfizer and Moderna vaccines carry exactly the same viral genetic material, and they differ only in how they get delivered to our cells once they are introduced in our body,” says Ramon Lorenzo Redondo, a molecular virologist at Northwestern University’s Feinberg School of Medicine. “The first dose primes the immune system, while the second one helps to rev it up. You can think of a paperback and a hardcover book. They are different in the outside but contain exactly the same information”, he says. “This genetic material, once introduced in our cells, makes them produce identical viral proteins. Therefore, it is expected that they will generate the same immune response.” — Ramon Lorenzo Redondo, PhD.

More quotes from experts

“There is no data on this, so you need to use judgment,” says John Moore, a vaccine researcher at Cornell University. “We would like to have data rather than use judgment. But we don’t have the luxury of data.” Moore says that if there were no alternative, he wouldn’t hesitate to mix the two vaccines. “We have to accept that we are in somewhat of an abnormal situation at the moment,” he says. — John Moore.

Conclusion/Data

I haven’t personally seen any data or controls for this. It is fascinating that some experts are willing to do this. We will just have to wait for more data to come out of the U.K. to solve this complex yet fascinating quagmire.

I’m building out this Python script exclusively for The Atlantic’s Covid 19 Tracking Project, which I am apart of.

Author(s) — Montana Mendy