As we saw from the previous diary, the normal incidence of anaphylaxis for the unadjuvanted seasonal flu vaccine is approximately 1 in 1 million vaccinations. However, officials are continuing to use the figure of 1 in 100,000 as reference. This is being repeated and reported faithfully by media in a game of 'telephone', such that no one appears to be asking where that number comes from and what exactly it measures. The PHAC website, however, does explain that figure as follows:
In any immunization campaign, from regular childhood vaccines to seasonal flu shots, the average reported rate of serious adverse events is about one case for every 100,000 doses distributed.
In other words, the 1 in 100,000 is
- for all serious adverse events (or AEs), not just anaphylaxis, and
- for all vaccinations, including many that cause higher AE rates in general, than flu vaccines
This is more than a little disingenuous IMHO, like comparing oranges to marshmallows. I suspect if this was a college paper it would have gotten a Fail, for violating some basic principles of epidemiology. That said, this revelation does serve a useful purpose - it verifies for me that I hadn't missed anything. It would seem that there is no data from anywhere that contradicts the abundance of evidence, that the risk of anaphylaxis from the seasonal flu shot is closer to 1 in 1 million than 1 in 100,000. Enough said!
At this point, it is still unclear whether these numbers (3 per million overall, and 38 per million with 1 lot) indicate a real safety issue fundamental to the formulation, or whether it is a batch-related or location-related anomaly. However, at least one other country is reporting increased incidence of allergic reactions including anaphylaxis.
From Sweden Summary of Adverse Drug Reaction reports in Sweden with Pandemrix received through November 20
The reporting pattern is generally consistent with what has been seen from previous clinical trials, with the exception of allergic reactions....Allergic reactions not previously seen in the clinical trials are now being reported as adverse reactions to Pandemrix. Similar allergic reactions have also been reported in other countries in Europe using Pandemrix.
From the tables on that page for Sweden, out of 1.9 million individuals vaccinated (some of whom may have received 2 doses), there were a total of 88 serious allergic reactions reported by HCWs and 6 reported by consumers, with 27 cases of anaphylaxis (3 anaphylactic shock). Which gives approximately 14 cases per million persons vaccinated.
So much for the status report. Now to the main focus of this diary. I've been reviewing the literature (remember the rabbit holes? LOL!) and found some really interesting information about oil emulsions and similar 'drug-delivery vehicles', the accompanying additives needed to stabilize such formulations, and the risk of anaphylaxis.
For those who don't already know this, the AS03 vaccine is supplied in 2 vials, one containing the split-virus antigen and the other containing the AS03 adjuvant, to be mixed before use. Once mixed, the preparation can be used for up to 24 hours. The AS03 adjuvant is a oil-in-water emulsion, containing the following, per dose. The first two are oils, the third is a surfactant (more here) used to stabilize the emulsion.
- squalene - 10.68 mg
- DL-alpha-tocopherol - 11.86 mg
- polysorbate 80 - 4.86 mg
As discussed before, emulsions are actually particles in suspension. In terms of size, both AS03 (150-155nm) and MF59 (165nm) belong to the submicron range. Although not considered 'nanoparticles' by the strictest definition, functionally they are often considered to be 'nanoemulsions'. (Fox 2009) At the nanoscale size, physical characteristics often play a much more important role than the molecular composition. So, the fact that these 2 vaccines are particles in suspension, makes them very different from the unadjuvanted vaccines, which are simply proteins in solution. This fundamental difference has major implications which we will explore below.
Anaphylaxis can happen via 2 mechanims: allergic or non-allergic (also known as anaphlactoid reaction). The allergic or IgE-mediated kind is the traditional one most people know about, where someone with tendencies towards allergies is sensitized by prior exposure, eg to egg proteins. As a result, they carry in their body IgE antibodies specific to that allergen. These antibodies are attached to the surface of mast cells, which are found in abundance underneath the skin, mucous membranes, and lining the outside of blood vessels. On re-exposure, the IgE binds to the allergen and activates the mast cell to release large amounts of pre-loaded molecules (eg histamines) that trigger the allergic response. The characteristics of the allergic reaction eg urticaria, or asthma, depend on the location of mast cell activation. Activation of mast cells lining blood vessels, by allergens in the blood, causes anaphylaxis. (See also this nice diagram from Janeway's Immunobiology.)
That is the traditional view of allergy and anaphylaxis. In recent years, however, there is increasing recognition that a substantial proportion of patients who suffer anaphylaxis do not have allergy in the traditional sense. Here is one example:
Seitz 2009 Vaccination-associated anaphylaxis in adults: diagnostic testing ruling out IgE-mediated vaccine allergy.
In the last 7 years all patients referred to our allergy clinic with a diagnosis of vaccination-induced anaphylaxis were subjected to allergologic diagnostic procedures to identify IgE-mediated allergy. We evaluated 38 patients with a history of vaccination-associated anaphylaxis. The diagnostic procedure included skin testing and challenge tests, i.e. re-vaccination with the suspected vaccine. In all 38 patients negative skin tests and tolerated challenge tests ruled out IgE-mediated allergic anaphylaxis to vaccine components.
So what causes the non-allergic kind of anaphylaxis? This is an area where the science is still under investigation. There are a number of possibilities including direct effect of some agents on mast cells and basophils, another kind of cell which can release the same molecules that trigger anaphylaxis. One area of immunology that is receiving renewed attention in recent years, is the activation of complement. The complement system is part of innate immunity, that responds to triggers immediately, within a matter of seconds. It consists of a series of enzymatic reactions between proteins and their receptors, each of which automatically triggers the next step, in a cascading fashion similar to what you see in the coagulation system. Mast cells and basophils (and possibly others) have receptors on their surfaces that can be activated by some products of the complement pathway, especially 2 molecules C3a and C5a, which are in fact called anaphylotoxins!
Here I'm going to digress a little and direct your attention to an interesting person, a Dr (formerly Colonel, US Army) Carl Alving, MD. Dr Alving has been mentioned in these pages before, in connection with the still-unsolved mystery, of the use of a cosmetics review paper as reference to support the safety of squalene, an ingredient in both AS03 and MF59. Let me give you some snippets, of Dr Alving's distinguished career, from his official bio:
He served on active duty in the U.S. Army Medical Corps from 1970-2000, and retired as a colonel. He was Chief of the Department of Membrane Biochemistry at WRAIR from 1978 to 2004. As a civil service employee he is currently Chief of the Department of Adjuvant and Antigen Research in the Division of Retrovirology at WRAIR....He has been an author or coauthor on approximately 270 scientific publications (200 peer-reviewed papers) in the fields of adjuvants, complement, lipid biochemistry and immunology, and liposomes as drug carriers and carriers of vaccines, and he sits on numerous editorial boards. He has created adjuvants for many types of experimental vaccines, including vaccines to malaria, HIV, biological threat agents, and prostate and intestinal cancer.
I'm telling you about Dr Alving because here's someone who has worked on creating oil-based adjuvants and drug-delivery systems for 30 years, so he ought to know a thing or two about them. Also because he is as pro-vaccine and pro-adjuvant as it gets, so I reckon he is most unlikely to over-hype any dangers with their use. Which made it very interesting when I discovered his name as co-author in a series of papers on a particular type of anaphylaxis:
Szebeni 2007 Animal models of complement-mediated hypersensitivity reactions to liposomes and other lipid-based nanoparticles.
Intravenous injection of some liposomal drugs, diagnostic agents, micelles and other lipid-based nanoparticles can cause acute hypersensitivity reactions (HSRs) in a high percentage (up to 45%) of patients, with hemodynamic, respiratory and cutaneous manifestations. The phenomenon can be explained with activation of the complement (C) system on the surface of lipid particles, leading to anaphylatoxin (C5a and C3a) liberation and subsequent release reactions of mast cells, basophils and possibly other inflammatory cells in blood.
We'll come back to the 'intravenous' part later. The authors have coined a new phrase, complement activation-related pseudoallergy or CARPA, to more accurately describe this type of anaphylaxis, which can happen with a broad range of pharmaceutical agents:
Szebeni 2005 Complement activation-related pseudoallergy: a new class of drug-induced acute immune toxicity.
The phenomenon is increasingly recognized as an immune toxicity issue that has particular significance in the modern field of pharmaceutical nanotechnology; R&D of particulate drug carriers, synthetic nano and microcapsules, liposomes and lipid complexes, micellar carriers and emulsifiers, new formulations of radiopharmaceuticals and contrast agents, etc. This increased awareness of CARPA is also reflected by the fact that testing for C activation in vitro and/or in vivo has become one of the immunotoxicology tests recommended by the US Food and Drug Adminsitration (FDA) that may be useful to identify the pseudoallergy potential of drugs, when needed.
The following table (adapted from Szebeni 2004) shows that the clinical picture of CARPA is almost identical to the allergic type of anaphylaxis. Treatment is also the same, the only differences lie in causation and mechanism.
Let me give a much simplified explanation of how CARPA happens. The complement system was evolved to respond to the presence of anything in the form of particles, by responding to anything that has a surface. Normal cell surfaces are protected from C activation by regulatory proteins, but foreign particles are not. In the case of lipid particles, Szebeni et al found that larger size, non-uniform sizes, charged particles, and high cholesterol content promote C activation, as compared to smaller, uniform and neutral particles. Also, while C activation happens in most patients as shown by blood tests, only a small proportion develop allergic reactions, possibly due to individual variations in the threshold for mast cell or basophil activation. Interestingly, they found that patients who do react tend to have history of other allergies in general, not necessarily to the particular drug being tested.
Lipid particles are not the only things in lipid emulsions that may predispose to anaphylaxis. Non-ionic surfactants such as polysorbate can also cause anaphylaxis by activation of complement (Tije 2003, Szebeni 2005) This is not unique to polysorbate, as you can see from the following chart.
Note that lipid particles or surfactants can cause anaphylaxis only if they are in the blood compartment, but not if they are given intramuscularly, at least in theory. In practice, high concentrations of anything in solution can diffuse into the blood, so that could happen in the case of polysorbate, but not for lipid droplets in emulsion.
A more likely possibility is inadvertent intravenous injection. How does that happen? Take a look at these instructions for intramuscular injections. After insertion of the needle into the muscle, the proper procedure is to pull gently on the plunger to see if any blood appears:
Step #18. Aspirate. If blood appears in the syringe, withdraw the needle, discard the needle/syringe set in a sharps container, and begin procedure again at step 9.
As stated on that page, this is a precautionary measure to prevent inadvertent intravenous injection, and is a very basic and universal practice. However, I spent some time the other day watching various videos of mass vaccination in Canada, and I can tell you that I was appalled, to see that the vast majority of injections were done without aspiration. Here's one video where you can see, at 1:30, 3 injections in a row, the first 2 without aspiration. Only the third one is done properly (btw it looks like this was done by the Ottawa Medical Director of Health, who was interviewed immediately after!) Then, at 2:02 again, another injection where the vaccine is pushed right into the patient without first testing whether the needle is in a vein or not!! I've looked at a few more videos, and they are more-or-less the same.
The risk of inadvertent intravenous injection is small but real. If you vaccinate enough people, it will happen to some of them, unless you do it right. Normally, for regular unadjuvanted vaccines that do not have the extra risks outlined above, it may not matter as much, but these are not normal times and the vaccines used are not normal vaccines!
Finally, as if all of the above is not enough, there is one more logistical component that can add to the risk of anaphylaxis, and that is the effect of inadvertent freezing of the vaccines. These vaccines have to be kept at 2-8°C throughout the distribution chain. Apparently, cold chain failures are shockingly common, even in developed countries. Here's a review by PATH:
Matthias 2007 Freezing temperatures in the vaccine cold chain: a systematic literature review.
This analysis highlights that accidental freezing is pervasive and occurs across all segments of the cold chain. Between 14% and 35% of refrigerators or transport shipments were found to have exposed vaccine to freezing temperatures, while in studies that examined all segments of distribution, between 75% and 100% of the vaccine shipments were exposed.
Freeze/thaw for any vaccine is bad, because it can affect the effectiveness of the vaccine, but in the case of oil-adjuvants, there is the additional risk of breakup of emulsion droplets during freezing and subsequent coalescence on melting.
Ghosh 2007 Factors affecting the freeze-thaw stability of emulsions
Freezing conditions cause the membranes surrounding individual droplets to rupture, allowing some oil-to-oil contact.....Ice is less dense than water, so will expand causing increasing internal stresses within the sample. The concentration of oil droplets in the unfrozen phase will also increase as the liquid water is removed.
Which is consistent with what Novartis says about MF59. As usual, no information about AS03 is available.
Ott 2000 The Adjuvant MF59: A 10-Year Perspective
Under stress conditions, such as prolonged exposure to high temperatures or freezing, large oil globules are formed. Storage of MF59C.1 under such conditions must, therefore, be avoided.
This is what it looks like, under the microscope. (from Ghosh 2007)
Oil coalescence results in formation of larger droplets of uneven size, which, according to Szebeni et al, is the perfect recipe for complement activation and anaphylaxis. Larger droplets also means reduced total surface area at the oil-water interface, releasing more surfactants which rises in concentration in the aqueous phase, again another risk factor in anaphylaxis.
In summary, in addition to allergy to vaccine components, the following factors can increase the risk of anaphylaxis for vaccines adjuvanted with oil-emulsions, like the AS03 vaccine. They are, of course, not mutually exclusive:
- Complement activation by lipid particles
- Complement activation by polysorbate
- individual susceptibility to complement activation related pseudo-allergy or CARPA
- inadvertent intravenous injection
- oil coaslescence after exposure to freezing temperatures
At this point, there's not a lot we can do about #1 to 3, but governments can surely step up staff training and supervision, and monitor every stage of the cold chain more closely, as a matter of priority. It's the least they can do, and what they should have been doing anyhow.... |
