What Are the Non-Specific Effects of Vaccinations?

Most of us are well aware of the risks (small) and benefits (big) of vaccines. That’s why we vaccinate our kids!

You probably aren’t aware that vaccines can also have non-specific effects.

What Are the Non-Specific Effects of Vaccinations?

Not getting measles after getting an MMR vaccine is a direct or specific effect of the vaccine.

“Vaccines are developed to produce an immune response to protect against specific disease targets. In addition to the specific effect of vaccines in reducing illness and death due to the disease targeted by the vaccine, some researchers have argued that there are additional “off-target” or “non-specific effects” (NSE) of vaccines, based on findings from observational studies. This refers to the potential effects besides the direct protection against the disease for which a given vaccine was developed.

In other words, NSE refers to any effect of a given vaccine, other than the intended effect of preventing disease caused by the specific pathogen they were designed to protect against. If present for a vaccine, NSE could potentially be beneficial, e.g. increasing protection against non-targeted infections, or disadvantageous, e.g. by increasing susceptibility to non-targeted infections.”

Non-specific effects of vaccines: Questions and answers

Not dying of another disease because you didn’t get measles would be a non-specific effect of the MMR vaccine.

It is also thought that the BCG vaccine might have a non-specific effect that protects you against other infections.

Are these non-specific effects real?

What about the studies that found the DPT vaccine could increase mortality from other infections?

Non-specific effects aren’t all positive…

The initial research on these non-specific effects of vaccines was done by Peter Aaby in Guinea-Bissau West Africa.

“A study in Guinea-Bissau published in the British Medical Journal in December 2000 suggested a nonspecific effect of routine vaccination that might influence survival in infants, either negatively or positively, depending upon the vaccine. Increased mortality was reported in children vaccinated with DPT in the 6 months following vaccination. Female gender was suggested as a modifier of the outcome.

GACVS reviewed this issue and urged WHO to arrange for testing of the hypothesis on different data sets from different countries where vaccination data, death, and other factors possibly influencing mortality had been recorded. Following an open call for proposals, WHO funded or cofunded studies in Bangladesh, Burkina Faso, Indonesia, and Papua New Guinea.

Analysis of those studies was completed: all of them showed reduced mortality in the children vaccinated with all of the vaccines. In particular, the studies showed no negative effect of DPT vaccination and no difference between males and females. Preliminary results of an independent analysis conducted to test the hypothesis on another six data sets have been communicated to GACVS. None of these confirmed the observations from Guinea-Bissau with respect to the DPT vaccine.

GACVS concluded that the evidence is sufficient to reject the hypothesis for an increased nonspecific mortality following vaccination.”

Potential adverse impact of routine vaccination

The Global Advisory Committee on Vaccine Safety of the WHO thoroughly looked into Aaby’s hypothesis.

It was rejected after further studies were done.

“The Global Advisory Committee on Vaccine Safety of the WHO, an independent group of experts in drug safety, vaccine science, and epidemiology that advises the Department of Vaccines and Biologicals of the organisation, has closely considered the reported findings and conclusions of the paper. It has found that numerous and serious deficiencies in the paper did not allow it to reach the same definitive conclusions reached by the authors. In particular, it found that the reported observations are incomplete and do not tally, no systematic effort has been made to address the likelihood of bias introduced by the method of data collection, and categorical inferences have been drawn from data that are either not significant or critically dependent on a very small number of results that might equally be explained by chance. In addition, the probability of the results being distorted by confounding factors has not been adequately addressed. The analysis was data driven and not based on a priori generation of a hypothesis, which makes interpretation of significance values and confidence limits problematic. The conclusions of this paper need to be scrutinised to the same extent as adverse events previously mistakenly attributed to diphtheria, tetanus, and pertussis vaccine.”

WHO responds to Guinea-Bissau report

And as Peter Aaby continues to publish new reports on the effects of the DPT vaccine in Guinea-Bissau, researchers have continued to investigate any possible role these non-specific effects might have on children.

The WHO Global Advisory Committee on Vaccine Safety has been reviewing the evidence on non-specific effects of vaccines on mortality since Peter Aaby published his initial research.
The WHO Global Advisory Committee on Vaccine Safety has been reviewing the evidence on non-specific effects of vaccines on mortality since Peter Aaby published his initial research.

One of the latest, a report to the Strategic Advisory Group of Experts (SAGE) on Immunization in 2014 concluded that the “data available do not provide conclusive evidence that the current schedule results in deleterious effects on all-cause mortality in children less than five years of age.”

This is mostly because studies about non-specific effects are thought to be weak and at high risk of bias.

What does this all mean?

It means that for now, we should likely stick with making our immunization decisions based on the direct effects of vaccines, knowing that they are safe, with few risks, and huge benefits.

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