How do the covid vaccines work? - How do the covid vaccines work updated 7
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2/3/21
How do the
covid vaccines
work?
Dr Nicky Funnell, clinical director
PMOA
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Firstly, some terminology
• Coronaviruses- a group of viruses with characteristic spike
proteins . We’ve known about for years, including some
common cold viruses. Sometimes a novel/new one
appears, jumping from animals to humans.
• SARS ( severe acute respiratory syndrome)- a particularly
nasty illness caused by a novel coronavirus named SARS-
CoV, which appeared in SE Asia in 2003 . It infected over
8000 people and killed over 700 before it was contained.
With a mortality rate of nearly 10% we had a lucky escape.
• Covid-19- a slightly less nasty illness caused by another
new coronavirus, originating we think in Wuhan, the virus
was given the catchy name SARS- CoV-2. As we know, this
one wasn’t contained
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How do pandemics end?-History and science shows a
number of possible endings, none of them quick
1.The virus mutates to become less infectious ( unlikely, they have a
survival instinct) or less lethal (more likely, but SARs-Cov 2 hasn’t
shown any sign of doing this)
2. The virus is contained, like SARs. This is only possible very early on
with local outbreaks, so won’t happen with covid.
3. The virus kills so many of it’s hosts that it’s got nowhere left to
spread- not a good outcome!
4. The virus infects so many of it’s hosts that it’s got nowhere left to
spread “herd immunity”; likely a long way to go to reach this for
Covid, and could still rumble on for many years and mutate
5. We find a treatment that means infections are no longer serious-
nothing highly promising found yet for Covid
5. a “ social end” rather than a medical end; society has enough and
decides to return to normal life. Not generally considered a good idea
for a potentially serious virus, but there’s only so many lockdowns that
society can withstand
6. We find a safe and effective vaccine. This is what happened for
smallpox and polio
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How do vaccines work?
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Which vaccines are
available?
• Pfizer- BioNTech official catchy name of BNT16b2; this is a
messenger RNA (mRNA)vaccine. This is the one that needs to
be kept super cold so it is difficult to transport to different sites,
and is the one that SLAM staff have been recieving
• Astra Zeneca “ The Oxford vaccine”-this is a conventional
vector vaccine , that can be stored at fridge temperature and
can be moved around to different sites. We may also get this
one soon.
• Moderna- this is another mRNA vaccine, approved last month
and likely to be available in the Spring
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How mRNA
vaccines work
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What is mRNA (messenger ribonucleic acid)?
• Our chromosomes contain double stranded DNA
• To make new proteins, the DNA unwinds and forms a
corresponding single strand of messenger RNA ( mRNA),
which codes for different amino acids.
• The amino acids group together to form different
proteins.
• The mRNA in the vaccines codes for proteins which
make spikes like the ones on the corona virus. By
themselves they are harmless, but our body sees the
spikes, thinks it’s seen corona virus, and produces an
immune response
• All our DNA is inside the nucleus of our cells, whereas
the decoding of the mRNA takes place outside the
nucleus. MRNA cannot get into the nucleus or affect our
DNA, and it breaks down after a few days and leaves our
body.
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The Oxford Vaccine
• It is based on a harmless adenovirus ( common cold virus) from a chimpanzee, which has been engineered
in the lab to include genes from Sars-Cov-2. So the vaccine is “pretend” SARs Cov-2. The spikes on the
pretend SAR-Cov-2 cause B antibodies and T killer cells to be formed, ready to spring into action for any
real infection. The deactivated adenovirus cannot reproduce and so is excreted from the body unchanged.
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• INGREDIENTS IN THE PFIZER- • INGREDIENTS IN THE ASTRA-ZENECA
What’s in the BIONTECH VACCINE
Covid-19 • mRNA
• Weakened adenovirus vector
• L-histidine
vaccines? • lipids and cholesterol • L-histidine hydrochloride
monohydrate
• potassium chloride
• magnesium chloride hexahydrate
• monobasic potassium
• polysorbate 80
phosphate
• ethanol
• sodium chloride
• sucrose
• dibasic sodium phosphate
dihydrate • sodium chloride
• sucrose. • disodium edetate dihydrate
• water for injections
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Which vaccine is better?
• Both vaccines offer a good level of protection against
getting covid. In the trials, the Pfizer vaccine gave
higher levels of protection, but both vaccines work
well and are safe, and I would be very happy to
receive either of them.
• Even in the small number of people where the
vaccine didn’t give them full protection , with both
vaccines for the thousands of people in the trail who
received a vaccine rather than a placebo, none
needed to be hospitalised due to covid.
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Priority Risk group
Residents in a care home for older adults and staff
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working in care homes for older adults
All those 80 years of age and over and frontline health
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and social care workers
When will I be 3 All those 75 years of age and over
offered a
All those 70 years of age and over and clinically
4 extremely vulnerable individuals (not including pregnant
women and those under 16 years of age)
vaccine? 5 All those 65 years of age and over
Adults aged 16 to 65 years in an at-risk group (see clinical
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conditions below)
7 All those 60 years of age and over
8 All those 55 years of age and over
9 All those 50 years of age and over
10 Rest of the population (to be determined)
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• Clinical conditions list for priority group 6
• •a blood cancer (such as leukaemia, lymphoma or myeloma)
• •diabetes
• •dementia
• •a heart problem
• •a chest complaint or breathing difficulties, including bronchitis, emphysema or
severe asthma
• •a kidney disease
• •a liver disease
• •lowered immunity due to disease or treatment (such as HIV infection, steroid
medication, chemotherapy or radiotherapy)
• •rheumatoid arthritis, lupus or psoriasis (who may require long term
immunosuppressive treatments)
• •have had an organ transplant
• •had a stroke or a transient ischaemic attack (TIA)
• •a neurological or muscle wasting condition
• •a severe or profound learning disability
• •a problem with your spleen, example sickle cell disease, or you have had your
spleen removed
• •are seriously overweight (BMI of 40 and above)
• •are severely mentally ill*
• *Individuals with schizophrenia or bipolar disorder, or any mental illness that
causes severe functional impairment.
• Adult carers
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• Can someone get Covid-19 from the vaccine?
• No, it is not possible to get Covid-19 from vaccines. Vaccines against SARS-CoV-2 use inactivated virus, or a
small piece of genetic code from a virus. None of these can cause Covid-19.
• How have the vaccines been developed so quickly?
• A lot of the work had already been done; the oxford team have been working on vaccines against
coronaviruses since the 2003 SARS outbreak. Scientists have also been developing mRNA vaccines for over 10
years. There have been lots of willing volunteers in a pandemic, and lots of opportunity for exposure to the
virus, meaning quicker results. Money was made available for research teams, scientists across the world
shared their findings. Also, some trials combined stages 1 and 2, and manufactured large quantities ahead of
approval. The bar for ensuring safety of a vaccine is higher than for a drug to treat an ill person and regulatory
approval is only granted if very high levels of safety are shown.
• Is the data accurate?
• The trials have been large, involving tens of thousands of people, but the major trials have not involved
purposeful exposure to covid. As such, the safety data is likely to be highly accurate but the effectiveness data
may change slightly as we get data from more people having the vaccine. However, from the current data the
effectiveness is likely to remain above that of many vaccines. For example, in the Pfizer trial which involved 44
000 people , 8 people who received the vaccine got covid, compared with 162 who received the placebo.
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Are there any serious side effects?
Trials from tens of thousands of people , from different age groups ( up to 85),
ethnicities and with different health conditions, have not shown any serious side
effects. With greater mass roll out of vaccines it is possible we will see rare reactions,
such as an allergy, but any risks appear tiny compared with the risks from getting
covid. The regulatory bodies will continue to monitor for any possible rare side effects.
Over 6 million people in the UK have now revived the vaccine without any major side
effects. Minor side effects are common and include a sore arm, body aches and a
headache, but these resolve within a day or 2.
Should I get vaccinated if I have allergies?
The MHRA temporarily advised that people with a history of severe allergy should not
receive the Pfizer vaccine. However, this advice was updated on 30th December when
they reviewed over a million people how had had the vaccine in the US and UK and It
found no evidence of an increased risk of anaphylaxis to the Pfizer vaccine among
people with serious but unrelated allergy histories. The current advise is that only
people who had an allergic reaction to the first dose of this vaccine, or who previously
had reactions to any of its components, should not receive it.
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I’ve had covid, do I still need the vaccine?
The vaccine is likely to offer longer and better protection than
having had covid alone, and indeed some people are now
getting covid for a second time, so the recommendation is to
have the vaccine if you have already have covid. Think yourself
lucky that you may have double protection!
Will the vaccine protect against the new variants?
Currently, it appears highly likely that the available vaccines
protect against the new variants circulating in the UK, but
scientists are continuing to monitor this, including the new
variants in brazil etc. It is possible that the vaccines will need to
be modified in the future to give full protection against future
new variants, as happens with the flu vaccine
I’ve got covid now, when can I have the vaccine?
You should wait at least 28 days from getting a positive test or
from your symptoms resolving if you are symptomatic.
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• Can I still get Covid if I’m vaccinated?
• In most people, the vaccines stopped them developing covid if exposed to the virus. In
the small number of people who did still get covid the illness seems less severe and
none were hospitalised
• Should I have the vaccine if I am immunocompromised?
• Yes, these are not live vaccines and if you are immunocompromised, including those
people with a low CD4 count, you can have the vaccine. However, your immune
response may not be as strong as other people, so you should still take precautions to
avoid exposure
• Should I get vaccinated if I’m pregnant or breastfeeding?
Although there are no known risks of giving vaccines to these groups, nor nay reason
why there would be a risk, but the data in limited. The current advice is that is
considered safe to have either vaccine whilst breast feeding, although an individual may
choose to defer the vaccine, and for pregnant women vaccination is generally not being
recommended although individual may choose to have the vaccine based on their
individual risks.
• Will we still need to wear masks and practice physical distancing once a vaccine is
available?
• Yes, until a larger proportion of the population is vaccinated and we are sure the
vaccine provides long-term protection. The more people who have the vaccine, the
quicker we will be able to ease these restrictions.
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• How long does it take to get immunity after getting the vaccine ?
• It takes approximately 2 weeks to get protection after the first vaccine.
• Why has the timing for the second dose changed?
• This was a decision made by the joint committee on vaccination and immunisation , as even by having
one dose you get a reasonable level of protection, and it is thought this approach will reduce deaths
from covid.
• I have a positive lateral flow test after the vaccine- has the vaccine caused this?
• No, the vaccine does not cause a positive lateral flow test, PCR test or common symptoms of covid. If
you have any of these you need to isolate, get a PCR test and contact your line manager
• Will we need to have an annual vaccine?
• We don’t yet know the answer to this question, and scientists will be continuing to monitor the long
term effectiveness of the vaccine and the possible need for an annual vaccine or a booster. Initial date
suggests that they antibodies produced by the vaccine are long lasting, but this will partly depends on
how much the virus mutates, and the more people who have the vaccine, the less chance it will have
to mutate.
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• Is the vaccine vegan?
• The vaccines contain no animal products. Both vaccines have been approved by the British Islamic
Medical Association
• Can the vaccines cause problems with fertility?
Claims of any effect of Covid-19 vaccination on fertility are not supported by any data. There is no
biologically plausible mechanism by which current vaccines would cause any impact on women's
fertility.
• What about possible long term side effects after 5-10 years?
No vaccines that have been developed have been shown to have any long term side effects, and the
way they work by boosting our immunity it is scientifically extremely unlikely they could cause any long
term side effects, especially as the vaccines are broken down and leave the body after about 5 days.
Whist some people may choose the “watch and wait” approach before deciding on a vaccine, this is a
risky strategy during a pandemic, when every day hundreds of people are dying from covid.
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• Risk of getting covid if you aren’t vaccinated:
moderate/high
• Risk of getting seriously unwell from covid:
moderate
In summary….
• Risk of getting covid if you are vaccinated:
low
• Risk of getting serious side effects from the
vaccine: very low
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• Pharmacy medicines information department 020 3228 2317
NHS https://www.nhs.uk/conditions/coronavirus-covid-19/coronavirus-
vaccination/coronavirus-vaccine/
Pregnancy advice
https://www.gov.uk/government/publications/safety-of-covid-19-
Useful Links vaccines-when-given-in-pregnancy/the-safety-of-covid-19-vaccines-
when-given-in-pregnancy
• https://www.vegansociety.com/news/news/vegan-society-response-
covid-19-vaccine
• https://britishima.org/pfizer-biontech-covid19-vaccine/
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