Claims about the Pfizer Covid-19 vaccine ingredients lack evidence

10 December 2020
What was claimed

The formation of “non-neutralizing antibodies” can lead to an exaggerated immune reaction, especially when the person is confronted with the real, “wild” virus after vaccination. This so-called antibody-dependent amplification, ADE, has long been known from experiments with corona vaccines in cats.

Our verdict

There’s no evidence antibody-dependent amplification is an issue in humans with Covid-19, and the use of plasma therapy suggests that it is not.

What was claimed

The studies into Covid-19 vaccines are too short to see if there are late effects. There were narcolepsy cases after the swine flu vaccination, and similarly this vaccine could put millions at risk.

Our verdict

It’s true that the swine flu vaccine was associated with a small increase in the risk of narcolepsy in children and young people. But the vaccine’s effects will continue to be monitored as it is rolled out, and so far it is not being given to children.

What was claimed

The mRNA vaccines from BioNTech/Pfizer contain polyethylene glycol (PEG). 70% of people develop antibodies against this substance—this means many people can develop allergic, potentially fatal reactions to the vaccination.

Our verdict

It’s true that the vaccine contains this, but in very small amounts. In some rare cases people are allergic to PEG and one study found 72% of samples were found to contain mostly low levels of antibodies against it, but that doesn’t necessarily mean that many will have an allergic reaction.

We’ve been asked to check a number of claims about the new Covid-19 vaccine and its ingredients.

Several websites have claimed the Pfizer vaccine contains “PEG” which could cause large numbers of allergic reactions, and also that the vaccine may cause infertility. The sites also claim any Covid-19 vaccine may make the disease worse, and that the studies are too short to check the vaccine is safe. There isn’t proper evidence behind any of these claims.

Polyethylene glycol

“The mRNA vaccines from BioNTech/Pfizer contain polyethylene glycol (PEG). 70% of people develop antibodies against this substance – this means that many people can develop allergic, potentially fatal reactions to the vaccination.”

It’s true that the BioNTech/Pfizer vaccine does contain polyethylene glycol (PEG). This substance is used in some vaccines but is safe in these quantities. It’s also safely used at higher concentrations as a laxative, and has a range of other uses from food to cosmetics.

It’s true that in rare cases people can have allergic reactions to PEG, but these are usually to medications where the PEG is the main ingredient, for example in solutions to prepare for colonoscopies. In the vaccine, PEG is just an “excipient”, so not an active ingredient that makes the vaccine work, but present in a small amount to allow the manufacture or storage of the vaccine.

A 2016 paper describes finding anti-PEG antibodies in 72% of the human samples tested, albeit mostly in very low levels. That doesn’t necessarily mean that many people will experience an allergic reaction.

The paper looks at the potential for PEG allergies in those who might be given therapeutics containing PEG. It concluded that “under certain threshold concentrations, low to perhaps even modest levels of circulating anti-PEG [antibodies] in most individuals would not adversely affect the safety and efficacy of PEG-modified therapeutics.”

At the time of writing, the MHRA have advised on a precautionary basis that people with “a significant history of allergic reactions” do not get the vaccine, after two NHS workers with a history of serious allergies had a reaction to the injection.

Antibody-dependent amplification

“The formation of so-called “non-neutralizing antibodies” can lead to an exaggerated immune reaction, especially when the test person is confronted with the real, “wild” virus after vaccination. This so-called antibody-dependent amplification, ADE, has long been known from experiments with corona vaccines in cats, for example. In the course of these studies all cats that initially tolerated the vaccination well died after catching the wild virus.”

Put simply, an antibody is made by the body’s immune system, and attaches to something on the surface of a virus, usually attacking it or rendering it harmless. Most vaccines work by giving the body a harmless version of a protein on the surface of the virus so it can make these antibodies, which would speed up the body’s ability to fight infection if it gets the real disease later. You can get these antibodies from having had the infection, having been vaccinated, or being treated with blood plasma from people who’ve had the infection which contain them.

“Non-neutralising antibodies” are antibodies that can attach to these proteins on the surface of a virus, but don’t actually kill or harm them. It has been found that in some cases in cats, they may actually help the infection take hold.

Antibody-dependent amplification, or ADE, is a very rare example of these non-neutralising antibodies making the infection worse. As well as some observations in cats, there’s solid evidence this happens in humans with Dengue fever

It’s true that a vaccine against a different kind of coronavirus in cats did kill those cats that were vaccinated sooner than those not. But the mechanisms of ADE are not well understood, and this could have been down to a number of different factors. 

Despite this, there isn’t much evidence that ADE is a problem in human coronavirus infections. ADE happening with a different disease in a non-human animal does not indicate it would happen in humans with a Covid-19 vaccine.

There is also quite substantial evidence that SARS-CoV-2 (the virus that causes Covid-19) antibodies don’t make the infection worse, due to the use of plasma from people who have had Covid-19 as a treatment for those suffering with an infection. Studies of how effective this is are ongoing, but if ADE were a risk here it’s likely that would have been observed by now.

Length of trials

“The much too short duration of the study does not allow a realistic estimation of the late effects. As in the narcolepsy cases after the swine flu vaccination, millions of healthy people would be exposed to an unacceptable risk if an emergency approval were to be granted and the possibility of observing the late effects of the vaccination were to follow.”

There are many reasons why this Covid-19 vaccine has been quicker to develop than any other vaccines. The vaccine has been trialled extensively as all vaccines are, but much of the analysis is happening simultaneously and being reviewed on a rolling basis, to speed things up due to the pandemic. 

There are other practical reasons it’s been so fast, for example the mRNA technology used meant testing candidate vaccines could start just days after the virus was genetically sequenced, and the familiarity of the virus, because of how closely it’s related to diseases like SARS and MERS.

When the Pfizer vaccine was approved in the UK, Prof Clive Page, President-Elect of the British Pharmacological Society said: “It’s important to note that in this case, speed was the result of focused and sustained effort in research, development and regulation – no safety shortcuts were taken.”

And as with all vaccines in the UK, its safety will be continually monitored as it is rolled out to the public, via the yellow card scheme (where information about potential side effects and adverse reactions are monitored and evaluated).

It’s true that the swine flu vaccine Pandemrix has been associated with a small increase in narcolepsy in children and young people. The vaccine was given to some healthy children and some young people particularly vulnerable to flu in the UK in late 2009, before studies in Finland emerged potentially linking the jab to the sleep disorder. 

A study in the UK later found that the risk of narcolepsy that could be attributed to this vaccine was between one in 57,500 and one in 52,000. Following a legal case, those who developed narcolepsy in the UK after getting the vaccine are eligible for compensation and it’s thought that around a hundred people in the UK were affected.

In the UK, the approved Pfizer Covid-19 vaccine is “not routinely recommended for children and young people under 16 years of age”. There may be some cases, for example, if children have complex needs and spend lots of time in specialised residential units where giving them the vaccine may be appropriate.

Infertility

“The vaccinations are expected to produce antibodies against spike proteins of SARS-CoV-2. However, spike proteins also contain syncytin-homologous proteins, which are essential for the formation of the placenta in mammals such as humans.”

There’s no evidence that the vaccine can cause infertility, and it almost certainly won’t. We’ve written extensively about this here.

Correction 22 January 2021

We previously wrote that we had not found evidence of 70% of people having antibodies against PEG. A reader pointed us towards such a study, and we have now included reference to that paper.

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