COVID-19 vaccine – What you need to know

The recent authorisation of the COVID-19 vaccine brings hope of a virus-free life in the New Year, but how likely is the return to normality in 2021?

The news of a vaccine against COVID-19 was welcomed with open arms at the start of December following the publication of Phase 3 trial results by Pfizer and BioNTech. Primary efficacy analysis demonstrated the vaccine is 95% effective against the virus at 28 days post-injection across gender, race and ethnicity demographics, and up to 65 years of age, at which point the efficacy of the vaccine dips to just over 94% (p<0.0001). This number was calculated from the total number of COVID-19 cases which emerged in the trial – 5% of which occurred in the vaccinated group (8 participants), and 95% in the placebo (162 participants).

The vaccine met the required safety data milestone presented by the FDA for the issue of an Emergency Use Authorisation (EUA) for individuals 16 years and older. The FDA has determined that the results of the Phase 3 trial provide clear evidence that the vaccine may be effective against COVID-19 and that the benefits of the vaccine greatly outweigh the risks. These risks, seen in ~3% of the 43,000 trial participants, include fatigue (3.8%) and headache (2%).

What’s in the vaccine?

The big question, and often the one with the largest scepticism, concerns the content of the vaccine. Most vaccines employ the use of an inactivated pathogen which triggers an immune response in a person’s body to produce antibodies. The new COVID-19 vaccine is based on a different mechanism which utilises the code which cells use to produce proteins. Messenger RNA (mRNA) vaccines have been developed for over a decade, containing within themselves single strands of RNA enclosed in lipid capsules. The COVID-19 vaccine contains mRNA which codes for the spike protein which the virus uses to enter human cells – it does not contain the live virus, therefore does not carry the risk of causing infection in the vaccinated individual.

The body’s enzymes read and translate the mRNA code to produce the spike protein, after which the mRNA is degraded. It is important to note that the mRNA does not enter the nucleus of any cell and does not alter the genetic make-up of an individual. The body’s immune system builds an immune response against the newly translated spike protein, resulting in the production of antibodies which can 1) tag the spike protein for destruction and 2) recognise the protein upon subsequent infection with the virus.

How long will immunity last?

Unfortunately, the length of the immune response is still unknown, and it will only become apparent once the participants of the trial begin to show a decline in serum antibody levels. The World Health Organisation (WHO) suggests a 6-month immune response would be acceptable to allow for a good chance of eradicating the virus. A recent study published in Science Immunology suggests that the immune response lasts ~8 months, in which case regular boosters may be needed to maintain immunity.

Was the rollout too quick?

From the outset, scientists knew that the only way of reliably combatting the virus would be the development of a vaccine. The readily available funding for global health emergencies such as this, and the huge number of volunteers willing to participate in the trial, was able to propel the pre-clinical and clinical testing of the COVID-19 vaccine.

In addition, the UK has its own regulatory body which had to approve the vaccine alongside the FDA before it was able to be introduced into the public. The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) agreed to give the COVID-19 vaccine accelerated EUA in the UK following the results of the Pfizer/BioNTech trial. Usually this process would take much longer, as drug regulatory bodies normally assess the results of a trial once it has ended – however, the MHRA has received regular chunks of data since October and has subjected it to ongoing review. The amount of data which the MHRA received is the same as other regulatory bodies, such as the European Medicines Agency, which begun the process of reviewing the data much later than the UK. For this reason, the UK received the vaccines much quicker than any other country.

What about the new strain?

The new strain of COVID-19 which is dominating parts of southern England brought concern to UK residents which had been celebrating the development of the vaccine moments earlier. BioNTech has confirmed with “scientific confidence” that the vaccine will work just as well on the new variant, and if needs arise, can be adapted to meet the new strain in 6 weeks. The proteins in the novel strain are 99% similar to the prevailing virus, and there is no detectable change in the spike protein against which the virus initiates an immune response. There is certainly no reason why infection by this new strain cannot be prevented by the vaccine despite its increased transmissibility. In the meantime, everyone should be practicing social distancing measures and correctly wearing masks to prevent further spread of the virus.

Reference: https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-conclude-phase-3-study-covid-19-vaccine

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