Serious adverse effects reported by the public after vaccination are thought to represent only 10% of the true rate of serious adverse events.
The Medicines and Healthcare products Regulatory Agency (MHRA) has specifically warned this estimate shouldn’t be used for Covid-19 vaccines, given there was high public awareness of its Yellow Card scheme.
Pfizer vaccine trials showed a 95% relative risk reduction in the development of infection against the ancestral, more lethal strain of the virus. However, the absolute risk reduction for an individual was only 0.84%.
These figures are correct, but relative risk reduction is most commonly used to communicate vaccine effectiveness as the way in which it is calculated means it is relevant no matter how prevalent Covid-19 is in the community. Absolute risk reduction is sensitive to the prevalence of the virus, so the figure measured during the trials may be less relevant to real-world situations.
A report by the Journal of the American Medical Association, looking at Covid-19 vaccination of children under five, showed that one in 200 had an adverse event that resulted in hospitalisation.
We could not fully replicate these figures from the study in question, but in any event it’s important to note the adverse events which were reported were not proven to be caused by the vaccine. The authors of the paper found the frequency of adverse events after Covid-19 vaccination was comparable with that after non-Covid vaccination.
The mRNA vaccines are not safe and not effective.
The vaccines used in the UK have all met the MHRA’s standards for safety and effectiveness, and it says the number of Yellow Card reports received so far is not beyond what was expected. Vaccine effectiveness has changed over the course of the pandemic, but they are still effective against hospitalisation and death.
Conservative MP Andrew Bridgen made a number of claims about the safety and efficacy of Covid-19 vaccines during a ’Vaccines: Potential Harms’ adjournment debate he raised in the House of Commons on 13 December.
Some of these claims were missing important context, so we’ve fact checked four of them in detail.
We have previously fact checked Mr Bridgen’s claims about Covid-19 vaccines twice in recent weeks—once when he made an inaccurate claim at Prime Minister’s Questions about vaccines during pregnancy and breastfeeding, and separately during a larger debate on Covid-19 vaccines.
We wrote to Mr Bridgen on both occasions to ask for a correction, but have not yet received a direct response and he is yet to correct either claim.
Here is our analysis of Mr Bridgen’s most recent claims in the debate on 13 December. Mr Bridgen has been contacted for comment.
Honesty in public debate matters
You can help us take action – and get our regular free email
Mr Bridgen said: “It is instructive to note that, according to pharmaco-vigilance analysis, the serious adverse effects reported by the public are thought to represent only 10% of the true rate of serious adverse events occurring within the population.”
Mr Bridgen's office has informed us this was based on an article about pharmacovigilance (the science of detection, assessment, understanding and prevention of adverse effects or any other medicine/vaccine related problem) published in an academic journal in 1995, which with regard to the UK’s Yellow Card scheme said: “Estimates of the completeness of reporting suggest that it is rare for more than 10% of serious reactions to be reported”.
The paper goes on to say that “reporting is rarely better than 2-4% for non-serious reactions”.
These figures have been shared more recently by the Medicines and Healthcare products Regulatory Agency (MHRA)—but as we have written before, the MHRA has also specifically warned against using these estimates in the context of Covid-19 vaccines.
In response to declining rates of Yellow Card reporting in 2018, the MHRA said: “It is estimated that only 10% of serious reactions and between 2 and 4% of non-serious reactions are reported”.
However, a notice now appears alongside this article which states: “These estimates should not be used as indicators of the reporting rate for Covid-19 vaccines, for which there is high public awareness of the Yellow Card scheme and the reporting of suspected reactions.”
Mr Bridgen also said Pfizer Covid-19 vaccine trials “did show a 95% relative risk reduction in the development of infection against the ancestral, more lethal strain of the virus.
“However, the absolute risk reduction for an individual was only 0.84%. In other words, from its own data, Pfizer revealed that we needed to vaccinate 119 people to prevent one infection.”
While these figures are accurate, it’s important to understand that absolute risk reduction and relative risk reduction measure two different things. (We have written about a number of very similar claims to this in the past, as absolute and relative risk reduction figures have sometimes been compared.)
Relative risk reduction describes how much less your risk is (of a specific outcome, for example, getting infected) if you’re vaccinated relative to someone who isn’t vaccinated, measured in percent.
So, hypothetically (these are not the actual figures), if the risk of getting Covid-19 for an unvaccinated person was 1% and the risk for a vaccinated person was 0.2%, the relative risk reduction would be 80% (as 0.2% is 80% less than 1%).
Absolute risk reduction, however, is the difference between the proportion of people who got sick in vaccinated and unvaccinated groups.
So in the same imagined example, the absolute risk reduction of vaccination would be 0.8 percentage points, as 0.2% (the risk for a vaccinated person) is 0.8 percentage points lower than 1% (the risk for an unvaccinated person).
Though it has been argued that both measures should be published, absolute risk reduction is dependent on the underlying level of risk at the time, so any estimate of absolute risk reduction of a Covid-19 related outcome is dependent on the prevalence of Covid-19 at the time.
This means the absolute risk reduction rate inferred from trial data is likely to be less relevant to the actual absolute risk reduction in real-world situations.
Mr Bridgen also added: “The World Health Organisation [WHO] and the Academy of Medical Royal Colleges have previously stated and made it clear that it is an ethical responsibility that medical information is communicated to patients in absolute benefit and absolute risk terms, which is to protect the public from unnecessary anxiety and manipulation.”
Mr Bridgen’s office indicated this referred to part of a journal article about understanding health statistics, published by the WHO in 2009, in which the author wrote: “I believe it is an ethical imperative that every doctor and patient understand the difference between absolute and relative risks, to protect patients against unnecessary anxiety and manipulation.”
The Academy of Medical Royal Colleges has also previously put out guidance stating that both absolute risk and relative risk should be published in press releases.
In a 2017 guidance document, the organisation said absolute risk reduction is “best understood by patients and the public”, while “relative risk reduction tends to exaggerate benefits and harms” and should not be used in isolation. However, the guidance also adds that the latter “is more generalisable as it does not depend on a specific time frame and baseline risk”.
Mr Bridgen also said: “In a Westminster Hall debate some weeks ago, I quoted a report by the Journal of the American Medical Association [JAMA] studying the effect of the Covid-19 mRNA vaccination on children under five years of age. It showed that one in 200 had an adverse event that resulted in hospitalisation, and symptoms that lasted longer than 90 days.”
We’ve not been able to fully replicate Mr Bridgen’s figures, with the study in question appearing to show that overall 10 out of 7,806 children (about one in 780) reported hospitalisations for suspected adverse events, though this figure would rise if you were to discount children who received lower dose vaccination. However in any event, Mr Bridgen’s comments are missing some important context.The study published by JAMA looked at events that occurred after vaccination, as Mr Bridgen said. But it’s important to note that these were not necessarily related to or caused by the vaccine.
The study also didn’t find that adverse events after Covid vaccination were more common than after other vaccination.
It said: “The overall frequency of adverse events after vaccination with [Pfizer’s Covid-19 vaccine] was comparable with the frequency of adverse events after vaccination with approved non–SARS-CoV-2 vaccines in children younger than 5 years.”
We fact checked Mr Bridgen previously when he made a claim about the same study during the Westminster Hall debate he references in his quote above. On that occasion he described some of the children as being “hospitalised with a vaccine injury”.
We said at the time that it was misleading to call these events “vaccine injuries”, and Mr Bridgen did not repeat this phrasing on 13 December.
Children under the age of five aren’t vaccinated against Covid-19 in the UK. As Mr Bridgen highlighted during his question, the Pfizer/BioNTech Covid-19 vaccine was authorised for use in infants and children aged six months to four years by the MHRA earlier this month, but it has not yet been recommended for use in this age group by the Joint Committee on Vaccination and Immunisation (JCVI).
Immediately after describing this study, Mr Bridgen said: “As the data clearly shows to anyone who wants to look at it, the mRNA vaccines are not safe, not effective and not necessary.”
As we have already said, the JAMA study did not prove that events recorded after the Covid-19 vaccine were caused by the vaccine, and the frequency of adverse events after Covid-19 vaccines was found to be comparable with those following non-Covid vaccines.
More generally, all the Covid vaccines used in the UK have met the MHRA’s standards for safety and effectiveness. The MHRA says: “The benefits of the vaccines in preventing Covid-19 and serious complications associated with Covid-19 far outweigh any currently known side effects. As with all vaccines and medicines, the safety of Covid-19 vaccines is continuously monitored, and benefits and possible risks remain under review.”
With regards to that monitoring, the MHRA says “the total number and the nature of the majority of Yellow Cards reports received so far is not unusual for a new vaccine for which members of the public and healthcare professionals are encouraged to report any suspected adverse reaction”.
A total of 53.8 million people in the UK have been vaccinated with at least one dose of a Covid-19 vaccine so far, with 40.4 million people having had their third dose or a booster.
As of 23 November 2022, the MHRA had received and analysed 177,925 UK Yellow Cards from people who have received the monovalent or bivalent Pfizer Covid-19 vaccine. These reports include a total of 511,776 suspected reactions, with a single report sometimes including multiple suspected reactions.
In the same time period, the MHRA received and analysed a total of 246,866 UK reports of suspected adverse reactions to the AstraZeneca vaccine, including a total of 874,912 suspected reactions, and 47,045 UK reports of suspected adverse reactions to the monovalent and bivalent Moderna vaccines, including a total 151,628 suspected reactions.
Where safety concerns have been identified, the MHRA and JCVI have launched investigations and issued advice.
Myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the protective sac around the heart) are recognised potential risks with the mRNA COVID-19 vaccines. According to the MHRA (as of 16 February 2022) the overall reporting rate across all age groups for myocarditis following vaccination with the Pfizer vaccine was 9 reports per million doses and for Moderna the overall reporting rate for myocarditis was 17 reports per million doses. As we’ve written before, Covid-19 vaccines have been listed as the underlying cause of death for some people, though we don’t have a breakdown of which vaccines were involved. According to the Office for National Statistics, there were 47 such deaths in England and none in Wales up to October. In Scotland there have been nine in the period up to November 2022. There has been at least one registered death in Northern Ireland up to the end of September 2022. It is possible that the UK total may rise, if there’s been a delay in registering some deaths due to the vaccines.
The MHRA has recorded 80 deaths from a type of blood clot that it has said may be linked with the AstraZeneca vaccine, but we can’t say how many of these were caused by the vaccine. Death certificates are the best source of data on deaths by cause.
Vaccine effectiveness has changed as new variants of Covid-19 have emerged, with Omicron—a milder variant of the virus—now the most prevalent strain in the UK.
The most recent vaccine surveillance report states that all three types of vaccine used in the UK have high levels of protection against death after infection with the Alpha and Delta variants. For those aged 50 and over, vaccine effectiveness against death from Omicron was around 50% 25 weeks after the second dose. At two or more weeks following booster vaccination, effectiveness was 93.6% against mortality while at 10 or more weeks it was 87.6%.
Among 18 to 64 year olds, vaccine effectiveness against hospitalisation with an Omicron infection after a booster peaked at 83.9% two to four weeks after booster vaccination, before dropping to 45.5% after 25 to 39 weeks. Vaccine effectiveness against the most severe hospitalisation outcome measured (those on oxygen, ventilated or in intensive care) ranged from 92.4% after two to four weeks down to 53.7% for 25 to 39 weeks following a booster vaccine.
For those aged 65 years and older, vaccine effectiveness against hospitalisation peaked at 89.5% before waning to 60.7% at 40 weeks or more after receiving a booster vaccine.
Protection against hospitalisation requiring oxygen, ventilation or intensive care ranged from 92.4% (two to four weeks after booster vaccination) down to 66.8% (25 to 39 weeks after booster vaccination) for older adults.
However the surveillance report found that levels of protection from the vaccine against symptomatic disease following Omicron infection are very low.
After we published this fact check, we contacted Andrew Bridgen to request a correction regarding his claim that serious adverse effects reported by the public after vaccination are thought to represent only 10% of the true rate of serious adverse events.
Mr Bridgen did not respond to our correction request.
Full Fact fights for good, reliable information in the media, online, and in politics.
Bad information ruins lives. It promotes hate, damages people’s health, and hurts democracy. You deserve better.