The Vaccine: What You Need To Know about BNT162b2
With the Pfizer/BioNTech Covid-19 vaccine being rolled out this week, we take a look at some of the key questions about how it works and the vaccination program
On 2nd December, the Pfizer/BioNTech vaccine (BNT162b2) was formally approved by the U.K.’s independent Medicines and Healthcare Products Regulatory Agency (MHRA). This is a remarkable feat of scientific endeavour, with less than a year passing by from the time of the virus first appearing to a vaccine being manufactured, approved and ready to deliver. However, it is perhaps even more astounding when we consider that the actual type of vaccine, based on mRNA, has not been widely used before.
How does BNT162b2 work, and why does it need to be frozen?
Most vaccines work by exposing the recipient to a weakened or inactivated form of a live virus, or to specific viral proteins that directly trigger an immune response. However, mRNA (messenger RNA) is, as its name implies, a template that is decoded to produce proteins. By exposing the body to viral mRNA, the viral proteins that this mRNA encodes (‘spike’ or coat proteins) are produced and expressed on the surface of the body’s immune cells, training the immune system to fight it before it encounters the real thing. The problem with mRNA is that it is inherently unstable and will be quickly destroyed if injected into the body. For this reason, BNT162b2 uses lipid (fat) nanoparticles to safely deliver the mRNA to the immune cells. To maintain this lipid system, the vaccine must be stored at -70 Degrees Celsius, requiring careful logistical planning for transportation and vaccine preparation. Once delivered, it can be stored in the fridge for up to 5 days. Individuals require two doses, on day 1 and day 21, with maximum immunity being acquired by day 28.
Does the vaccine work in the elderly?
Yes. Given the dampened immune response that the elderly show to many infections (including their response to some vaccines), this is an important question. Out of around 18,000 people who were given the vaccine, 22% were over the age of 65. To quote the MHRA analysis:
“In participants 65 years of age and older and 75 years of age and older without evidence of prior infections with SARS-CoV-2, efficacy of COVID-19 mRNA Vaccine BNT162b2 was 94.7% (two-sided 95% confidence interval of 66.7% to 99.9%) and 100% (two-sided 95% confidence interval of -13.1% to 100.0%) respectively”
It should also be noted that the vaccine was effective in a range of ethnic groups and in those with different co-morbidities included in the trial.
Are there any side effects?
As with most vaccines, common side-effects reported included fatigue (60%), headache (50%), muscle aches and pains (30%) and a temperature (10%). Due to limited data, the vaccine will not be given to those who are pregnant or breast-feeding, or those under age 16.
Does it stop people catching the virus and passing it on to others?
We don’t know. The study was designed to look at whether the vaccine prevented symptomatic Covid-19 infection. It is much more difficult to determine whether a vaccine stops viral transmission to others unless we know precisely when people were exposed, all potential contacts of people in the study are themselves tested and at the right time, the tests are 100% accurate etc…but more information on this will hopefully emerge.
Who will be vaccinated in the U.K.?
The U.K. has ordered 40 million doses of the vaccine. Since each person needs two doses, this is enough to vaccinate 20 million people. Given that practically every country in the world will be trying to acquire the vaccine, the supply chain may struggle to keep up! The Joint Committee on Vaccination and Immunisation (JCVI) will recommend a priority order, to be decided by the government, which is set to include elderly people in care homes and care home staff, followed by the over-80s and health and care staff. It is expected that the majority of the population will be vaccinated next year, although England’s Deputy Chief Medical Officer, Professor Jonathan Van-Tam, said “If we can get through phase one [of the priority list] and it is a highly effective vaccine and there is very, very high up take, then we could in theory take out 99% of hospitalisations and deaths related to Covid 19”.
Whilst the vaccine could spell the beginning of the end for our Covid-19 nightmare, we are not yet out of the woods. It will take several months to vaccinate everyone and we are just entering Winter, a time when the NHS struggles to cope even in a ‘normal’ year.
But there is certainly light at the end of the tunnel.
Please note that the views expressed here are those of the author alone and not necessarily those of any other person or organisation.