Three Vaccine Doses Increase Infection Risk by Up to 27%, Study Finds

Image Credits: juanma hache / Getty Images .

Three doses of the Moderna Covid vaccine increase your risk of Omicron infection by up to 27%, a study has found.

The pre-print study (not yet peer-reviewed) was funded by Moderna itself and partly designed by employees of Moderna as well as involving researchers from Kaiser Permanente in Southern California. The study’s reporting of poor outcomes for the original vaccine may be understood in the context of Moderna now having a ‘bivalent vaccine’ which targets Omicron.

The study used a test-negative case-control design to evaluate the Moderna Covid vaccine’s effectiveness against infection and hospitalisation with Omicron subvariants. It included 30,809 test-positive and 92,427 test-negative individuals aged over 18 years tested during the first half of 2022. Results were adjusted for potential confounders such as age, sex and comorbidities.

The study found negative effectiveness (i.e., where the vaccinated have a higher infection rate than the unvaccinated) for three doses against all Omicron subvariants (BA.2, BA.2.12.1, BA.4 and BA.5) except BA.1, where the waning was slower.

Vaccine effectiveness against infection was negative within five months (150 days) at around minus-25%, meaning there were 25% more infections in the vaccinated than in the unvaccinated. The results are shown below and I’ve marked the five-month figures in red. The lowest figure was for BA.2.12.1 at nearly minus-27%.

A second recent study from Sweden (also in pre-print) also showed negative vaccine effectiveness against Omicron, this time for two doses and after just 15 weeks, with the trend moving deep into negative territory (see below). The study looked at all Swedish data from December 27th 2020 to January 31st 2022, meaning for Omicron it only covered BA.1.

The Sweden study also showed vaccine effectiveness against hospitalisation and death heading into negative territory after about a year (see below; hospitalisation top, death bottom) – though this chart makes use of a spline curve, which the authors note may differ from the other data at later time points as it “assumes a linear association in the tails” and also due to the low number of data points.

One oddity about the Sweden study is that for pre-Omicron it claims to show a high and non-waning vaccine effectiveness, as shown below.

This implies that the vaccine effectiveness remained over 90% for nearly a year. This is very strange, as a study from Sweden using the same data but published in October 2021 found a sharp decline into negative territory by eight months.

Why does the new Sweden study, using the same population data, find such a different trend of vaccine effectiveness pre-Omicron? On the face of it it makes no sense. Dr. Clare Craig commented to me that it appears (in Table s8) the authors used as a reference only one value for the unvaccinated, which had huge numbers of patients in it, suggesting they are using winter Covid in an unvaccinated population as their baseline rather than the unvaccinated levels at a similar point in time. She notes that rather than comparing with the unvaccinated, if you compare the figures for the periods after vaccination with each other then the test positivity goes from 0.01% up to 0.8% as time passes, indicating a waning vaccine, in contrast to the non-waning vaccine presented in the chart.

It’s worth noting that a recent study from Oxford University found a similar negative vaccine effectiveness pre-Omicron in England data.

Why the picture of the vaccines we are gaining from studies isn’t always consistent is not really clear. However, what is clear is that a number of studies are now showing negative effectiveness, including studies from the manufacturers and pharmaceutical companies themselves. This is worrying as it raises questions of what may be causing it (assuming it is a real phenomenon and not an artefact of some kind). Is it due to immune imprinting (‘original antigenic sin’) impeding the response to later variants, or a more general inhibition of the immune system, or something else? Whatever it is, it is highly disturbing to think that the vaccines may increase susceptibility to infection, and even more disturbing to think that the official solution put forward to address this problem is an endless series of further vaccine doses.



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