What are the differences between the COVID vaccines?

Vaccines have come a long way from the days of Edward Jenner and Louis Pasteur. In fact, when it comes to COVID vaccines, countries are spoiled for choice- a race amongst drug companies to produce a vaccine has left us with a few different options.

You’ve likely heard of the main players by now, but are there any differences between the major COVID vaccines? The short answer is yes; the differences between the vaccines are relatively significant and certainly give us plenty of reasons to be optimistic about combating COVID in 2021.

Pfizer-BioNTech

pfizer covid vaccine
Source: Justin Tallis / Getty

A collaborative effort between American pharmaceutical giant Pfizer and the Germany-based biotech company BioNTech, the Pfizer vaccine was the first to receive approval and be distributed in the UK.

Starting with the good: the Pfizer vaccine is a messenger RNA (mRNA) vaccine. Without infuriating any immunologists (I hope), what this essentially means is that the mRNA in the vaccine provides a blueprint to your cells on how to pre-emptively produce antibodies to fight off COVID.

This stands in contrast to traditional vaccines, which work by introducing a weakened live version of the virus into your body, which in turn produces antibodies. Traditional vaccines work wonderfully too, but mRNA vaccines should be easier to adapt to deal with any potential mutations which render the old doses ineffective.

Turning to the weaknesses: the Pfizer vaccine requires ultracold storage (roughly -70 °C) until thawing, usually within five days of the administration, to remain effective. To see what this whole process actually looks like, Pfizer has provided some videos and guidance here for your viewing pleasure.

The Pfizer vaccine boasted a 95% success rate after two doses in EU trials, with the usual and expected side effects of pain, dizziness, and fatigue taking place. A few suffered anaphylactic reactions, but the current advice is that the vaccine is fine to take, as long as you’re not allergic to one of the components.

Moderna

Moderna COVID vaccine
Source: Getty

The Moderna vaccine was developed by (spoiler alert) the American pharmaceutical company Moderna, in collaboration with the U.S. Department of Health and Human Services. The Moderna vaccine received approval for use in the UK on January 8th, the last of the big three currently in use.

Like Pfizer, the Moderna version is an mRNA vaccine and boasts a similarly high success rate at 94%. The primary difference between the two is that the Moderna vaccine can be stored at -20°C , making the logistics around transport significantly less of an issue, particularly for low-income countries.

Moderna are also exploring the possibility of studying the effects of a third booster shot as more data is collected on the longevity of antibodies. Further research is also likely to be done into the effectiveness of the vaccine on children, as this has not been an area of pressing concern for any of the developers, or of the states administering them.

Oxford-AstraZeneca

astrazeneca covid vaccine
Source: Dado Ruvic/Reuters

The current pride of the nation, the AstraZeneca vaccine was developed by Oxford University in collaboration with the British-Swedish pharmaceutical company AstraZeneca. It’s first non-trial administration took place in the UK on January 4th, and doses of the vaccine have started to be distributed worldwide.

Unlike the Pfizer and Moderna variants, the AstraZeneca version is a traditional-style vaccine developed from a modified chimpanzee adenovirus. The big upside here is that the vaccine can be stored at ‘fridge temperature’, making it significantly easier to handle in local doctors’ surgeries, and in pharmacies.

Clinical trials suggested an immunisation rate of 90% when participants were initially administered a small dose, followed by a full dose four weeks later. This stood in clear contrast to the 62% efficacy rate reported when the initial dose was a full dose, also followed by a full dose administered a month later. Further research as to the significance of these findings is ongoing, although use of the vaccine is certainly well underway.

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