IS it Safe? Mixing COVID-19 vaccine Schedules

The New York Times blunders, fans of chaos narratives stoke the flames

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On mixing vaccines.

The New York Times recently published a story based on a misreading of the UK's Green Book on vaccinations. In the story titled 'Britain Opens Door to Mix-and-Match Vaccinations, Worrying Experts' they:

  • Say Britain has quietly updated their vaccination playbook to allow for a mix and match regimen of vaccines.

  • Say this contradicts CDC advice.

  • Say the UK emergency green-lighted two vaccines (In fact, they went through our normal regulatory assessment process).

  • Have 4 US experts chime in with "We're kind of in the Wild West" and Officials in Britain “seem to have abandoned science completely now and are just trying to guess their way out of a mess.”

Advice. If a journalist rings you up for a quote as an academic, even the New York Times, ask them what they think is happening and their evidence, then tell them you will ring back after you have independently verified what they are saying. You may be being used.

Is the New York Times right?

So what do UK authorities actually say? Has the UK opened the door to the mixing vaccines? Part 2 of the Green Book has section called Information for public health professionals on immunisation, Chapter 14a is on COVID-19. The general guidance at no point says anything about routinely mixing the vaccines as policy. It is an extensive technical walkthrough of the disease, vaccine schedule, and dosing that a competent UK healthcare professional would be able to follow.

There is a section on Previous Incomplete Vaccination in the COVID-19 Chapter . Although the UK does have good clinical record keeping, there are always circumstances that arise which do not fit with clinical guidance. What if someone was vaccinated in another country and turned up for the second dose and didn't know which vaccine they had been given? There will be rare cases were records have failed. What does a professional do then? The Joint Committee on Vaccines and Immunisations gives healthcare professionals in that situation advice.

If the course is interrupted or delayed, it should be resumed using the same vaccine but the first dose should not be repeated. There is no evidence on the interchangeability of the COVID-19 vaccines although studies are underway. Therefore, every effort should be made to determine which vaccine the individual received and to complete with the same vaccine. For individuals who started the schedule and who attend for vaccination at a site where the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer one dose of the locally available product to complete the schedule. This option is preferred if the individual is likely to be at immediate high risk or is considered unlikely to attend again. In these circumstances, as both the vaccines are based on the spike protein, it is likely the second dose will help to boost the response to the first dose. For this reason, until additional information becomes available, further doses would not then be required.

Healthcare professionals reading this are unlikely to start deciphering the text like a lawyer, torturing the text to fit the argument. The guidance makes three clear statements that vaccine mixing is not routine (my emphasis above). After all else has failed, in individual cases, then the option exists to offer the alternative vaccine. To suggest that healthcare professionals will read this guidance as suggesting they can willy nilly mix vaccines means that you’d have to attribute a level of incompetence in UK healthcare professionals that does not exist.

The Guidance is clear. Don't mix vaccine types, except in these specific circumstances.

Added to this, on the 30th of December Simon Stevens, Chief Executive of the NHS, wrote to all the areas of the NHS that might be involved in vaccinations stating "Each person's second dose must be from the same manufacturer as their first dose."

Could this be any clearer?

Other concerns that have come up on twitter?

  • In a chaotic vaccination centre people this guidance will be used to give which ever one is lying around.

  • In a chaotic vaccination centre there will be poor record keeping, so this guidance will be used all the time.

  • We'll run out of vaccines, and have to mix vaccines.

This stuff is coming from people stoked up on twitter, who haven't seen how vaccinations centres work and seem to want to will chaos into being to fit their narrative that the UK is useless. Much of it reads not as people with concerns, but people trying to manufacture concerns.

The cinematic version of the pandemic is a maelstrom of chaos, which while I understand where it comes from, doesn't exist. Even in the movie Contagion, the vaccination lines and centres looked fairly orderly.

My pre-academic background was as hospital pharmacist. I can tell you that hospital pharmacists involved in this will be absolute sticklers when it comes to following the guidance. Nurses and clinicians will be sticking to guidance. Vaccinators will be working under close supervision.

The editor of the BMJ has now written to the New York Times asking them to correct their report, and here is Public Health England's Head of Immunisations Dr Mary Ramsey on mixing vaccines.

Dr Mary Ramsay, Public Health England's head of immunisations, said: "We do not recommend mixing the Covid-19 vaccines - if your first dose is the Pfizer vaccine you should not be given the AstraZeneca vaccine for your second dose and vice versa."

Dr Ramsay added that on the "extremely rare occasions" where the same vaccine is unavailable or it is unknown which jab the patient received, it is "better to give a second dose of another vaccine than not at all".

You can also hear the Deputy Chair of the Joint Committee on Vaccination and Immunisation clearly state what the policy currently is (Click on tweet for audio).

Paper of record?

I'm not an expert on the The New York Times, but it does appear to have an ideological lens focused on the UK. There is a view that Trump-Bolsonaro-Johnson form a populist trifecta that always have to be wrong. Even if that is true, and Johnson seems qualitatively different from the other two, the JCVI and MHRA make independent non-political judgements. Johnson and the rest of the UK government has been very careful to defer to experts on evidence for therapies for Covid in government briefings. In contrast, Trump was willing to give advice on disinfectants, hydroxychloroquine, and 'light inside the body'.

The UK has also run one of the biggest trials of treatments for COVID-19 (RECOVERY) and the Oxford AztraZenaca vaccine trials (There have been criticisms of trial management in the latter case, but fundamentally amazing science). We are not 'abandoning science' as one of the quoted experts in the New York Times suggested.

Anti-Vaccine adjacent

I've spent a lot of time countering anti-vaccine groups over the past 20 years, mainly around the MMR hoax. The New York Times piece fed directly into scare-mongering tweets from blue-check twitter users with tens of thousands of followers. What is interesting about these people, is that they don't consider themselves anti-vaccine as they spread misinformation and seemingly wilfully misinterpret or remove the context of technical documents to fit their agenda. They are using vaccine policy as a political weapon. I am not sure this makes them much better than anti-vaccinators, who tend to focus on quack science, long standing tropes, and a broader anti-establishment view rather than specific political lens. While there were rogue MPs who were anti-MMR during the 2000s and 2010s, the anti-MMR movement wasn’t as politically orientated as this one. And it is a complicated picture, while it is political in nature, it seems spread across the left and right in slightly different forms. At least on twitter, this looks in part to be a side effect of the way the platform incentivises types of outrage.

If you are feigning concern about public confidence in vaccines while continuing to spout politically motivated vaccine disinformation, it may not make you an anti-vaxxer, but you are adjacent.

How much of this will bleed into public consciousness out of the echo chamber of social media we can’t be sure, but let’s be clear, it was a mainstream publication that started this particular vaccine discourse.


Trust is essential to vaccines programmes. You should have a high bar for making claims in this area.

That applies to newspapers and twitter celebs.

It's also not enough to say that government has to be careful about messaging, although they should be. If you write good faith advice in a technical document for health professionals, it is had to control for the media wilfully misinterpreting it for clicks.

And as we have found since 2016 with Trump, we can find today with the New York Times.

There's always a tweet.


Stay safe.


Don’t forget to report your suspected adverse effects from medicines. In the UK, this is the Yellow Card Scheme