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Health Shot: Vaccines

January 10, 2020

 

I’m sure we can all remember that dreaded moment at the doctor’s office when they say “Time for some shots!”. Much crying later (maybe that’s just me) , we leave the office with a brightly colored band aid – and sometimes a sticker for the road. But what exactly goes on in these shots we receive from such a young age? What do these vaccinations do in our bodies? Moreover, what explains the origins of the the anti-vax movement?

What happens when we get sick?

When bacteria and viruses enter the body, immune cells called help fight off these invaders, which are called antigens. These antigens trigger the response by the body to fight them off with T Cells and B Cells. B Cells make antibodies, which are proteins produced by our immune system that help attack the antigens. Each antibody fits like a puzzle piece with a particular antigen and blocks off the antigen from communicating with other cells. This causes the antigen to die off. T Cells secrete chemical signals in the body that let other immune responses know to activate. Once the body has begun to eliminate the microbes faster than they reproduce, and the disease is eliminated, some of the T and B cells convert into memory cells can recognize the infectious microbe if it appears again and appropriately release antibodies. This offensive cycle of recognize, react, and remember allows our body to be very effective in responding to bacteria and viruses we interact with every day.

How do vaccines help?

Vaccines allow the body to be exposed to an illness and developed the memory cells, so that when we are exposed again to the microbe, we can quickly react. The vaccine contains a weakened form of the virus that does not cause the disease or reproduce very well – but this enough to get our bodies into action. Following the same cycle as above, the body fights off this weakened disease and is left with the memory T and B cells that cause future protection. Since the disease is in weakened form, many vaccines require more than one dose. In the case of the flu vaccine, the CDC recommends a vaccination every year since the vaccination is updated each year to include the strains that research suggests would be most pervasive that flu season.

Where did the Autism-Vaccine link come from?

In 1998, Andrew J Wakefield along with 12 co-authors published a study suggesting that from 12 cases, they found links between the MMR vaccination and autism in The Lancet. Though the paper could not support a causal relationship between the MMR vaccination and autism, in a video Wakefield suggested that the risk of autism was developing with the combined MMR vaccines. The press reaction to the publication and Wakefields statements were immediate, and parents in Britain and the United States began to delay vaccinations for their children.

Ideas Debunked:

In 2004, the editor of the Lancet revealed that the Wakefield has been paid by attorneys looking to file lawsuits against vaccine manufacturers, demonstrating a clear conflict of interest and ulterior motive. In 2010, after many of the co-authors had redacted their statements in the paper, The Lancet redacted the paper itself.

In 2011, The British Medical Journal published a report by Brian Deer who investigated how Wakefield could have made the statements he did in the 1998 paper. Deer found that while the paper claimed eight children showed autism-like symptoms days after the vaccination, in fact only two showed symptoms that they had even before the vaccine was administered. With all this evidence, researchers agree that the original study should not have been published as the results could be categorized as research fraud.

After the MMR-Autism hypothesis was no longer held, critics cited thimerosal, a preservative containing mercury as a possible cause for autism. In the late 1990’s concern for eating mercury present in a different form in fish heightened, and people turned their eyes to the mercury used in vaccines. A final report published in 2004 by the Institute of Medicine rejected an association between thimerosal and autism. However, today most childhood vaccines no longer contain thimerosal.

Since autism rates have continued to increase since the onset of routine vaccination, critics continue to question vaccines. Research from the Autism Speaks associate reveals that autism is causes by both genetic and environmental factors. The exact reason why autism develops is still unclear, but vaccinations have been currently ruled out as a cause.

The Anti-Vax Movement:

In 2007, celebrity Jenny McCarthy’s son was diagnosed with Autism, and she blamed the diagnosis on the effect of vaccinations. This essentially kickstarted the recent anti-vax movement again, though the movement has been in existence since vaccines were widespread. The recent advent of Facebook and twitter has increased the spread of misinformation and has increased vaccines refusal across America. With the popularity of the anti-vax movement, the herd immunity of our population is threatened. For highly contagious diseases, herd immunity is achieved when 90-95% of the population is vaccinated. For less contagious diseases, like polio, 80-85% is enough. Herd immunity is precisely why anti-vax movement affect those who still choose to get immunized. Turning into a Tragedy of the Commons, one  misinformed individual can affect the health safety of their surrounding community. For this reason, staying informed with well established facts, rather than opinions, is important when dealing with medical issues.

Sources:

Vaccines Protect Your Community. (2017, December). Retrieved March 10, 19, from https://www.vaccines.gov/basics/work/protection

How Do Vaccines Work? (2019, April 09). Retrieved from https://www.niaid.nih.gov/research/how-vaccines-work

Understand how Vaccines work. (2018, July). Retrieved from https://www.cdc.gov/vaccines/hcp/conversations/downloads/vacsafe-understand-color-office.pdf

Do Vaccines Cause Autism? (n.d.). Retrieved from https://www.historyofvaccines.org/content/articles/do-vaccines-cause-autism

Wakefield, A. J. (1999). MMR vaccination and autism. The Lancet,354(9182), 949-950. doi:10.1016/s0140-6736(05)75696-8

 

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.