tag:blogger.com,1999:blog-7882528729236683983.post5538175464045264086..comments2023-10-18T00:44:23.818-07:00Comments on Fully Vaccinated: Community immunity (herd immunity)Matthew Rollossonhttp://www.blogger.com/profile/13379845581992276704noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-7882528729236683983.post-22948195500088640022015-02-20T20:14:33.586-08:002015-02-20T20:14:33.586-08:00Thank you, Matthew. This helps a lot. I'm sure...Thank you, Matthew. This helps a lot. I'm sure I will be directing a lot of folks to this response!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7882528729236683983.post-71408279758368219152015-02-20T18:27:01.705-08:002015-02-20T18:27:01.705-08:00Thanks for reading it and thank you very much for ...Thanks for reading it and thank you very much for your comments and questions!Matthew Rollossonhttps://www.blogger.com/profile/13379845581992276704noreply@blogger.comtag:blogger.com,1999:blog-7882528729236683983.post-42434149609738254432015-02-20T18:23:29.129-08:002015-02-20T18:23:29.129-08:00Joy,
I've heard that argument before. Let me ...Joy,<br /><br />I've heard that argument before. Let me start by saying that all vaccines are not created equal.<br /><br />For most people, immunity to measles from MMR appears to be life-long. MMR is a live attenuated (weakened) virus vaccine. The vaccine viruses behave like wild-type viruses without causing disease. That means that our immune responses to live virus vaccines are identical to the responses to natural infection. Specifically, live virus vaccines induce both antibody-mediated and cell-mediated immune responses. Serum antibody titers to measles wane over time but cell-mediated immune memory is much more persistent. Most vaccinated people who are exposed to measles virus (vaccine or wild-type) have an anamnestic response – their serum antibody titers shoot up almost immediately.<br /><br />Some people mistake the second dose of MMR for a "booster." It's not. Around 92% of people develop immunity to measles with one dose of MMR. Around 98% develop immunity to two doses. The second dose is given to increase the number of people who are immune to measles, not to "boost" the antibody titers of those who are already immune to the disease.<br /><br />The fact that both measles and rubella have been eliminated from the U.S. is evidence of herd immunity. Yes, there are primary and secondary vaccine failures, but measles transmission in this country is not sustained.<br /><br />Immunity to bacterial diseases is different. Immunity to pertussis is not permanent. People who get pertussis can get is again. On the other hand, humans do not develop immunity to tetanus or diphtheria from natural infection. Tetanus and diphtheria toxoids (vaccines) produce immunity to those diseases that nature doesn't give us. Nevertheless, immunity from DTaP/Tdap wanes.<br /><br />Pneumococcal, meningococcal, and Haemophilus influenzae type B (Hib) vaccines target polysaccharides (sugars) on the surfaces of those bacteria. Those polysaccharides are poorly immunogenic; that is, they don’t stimulate a strong immune response. Not only that, but there are a lot of different types of pneumococcal, meningococcal, and Haemophilus influenzae polysaccharide capsules and they are not cross-reactive: immunity to one doesn't confer immunity to others. Conjugated pneumococcal, meningococcal, and Hib vaccines use bacterial polysaccharides that are attached (conjugated) to another immunogenic material like tetanus toxoid or diphtheria toxoid. This stimulates both cell-mediated and antibody-mediated immunity. There are a number of studies that have demonstrated reductions in disease in non-immunized adults after the introduction of childhood immunization with conjugate vaccines – herd immunity.<br /><br />Influenza is a different animal because the antigens on the surface of influenza A viruses mutate almost continuously. Nevertheless, there was a study in Canada that showed that immunizing children against influenza protected adults who were not vaccinated which, by definition, is herd immunity. http://jama.jamanetwork.com/article.aspx?articleid=185509<br /><br />In short, what is true for one vaccine is not true of all vaccines. I've heard people say that most people who get measles have been vaccinated. That's not at all true. People who say that are confusing measles with pertussis (please see my post on attack ratios: http://fullyvaccinated.blogspot.com/2012/04/attack-ratios.html).<br /><br />I hope this helps.<br /><br />Matthew<br />Matthew Rollossonhttps://www.blogger.com/profile/13379845581992276704noreply@blogger.comtag:blogger.com,1999:blog-7882528729236683983.post-22492856647783534332015-02-20T17:40:10.425-08:002015-02-20T17:40:10.425-08:00Also, thank you for this blog. So many great infor...Also, thank you for this blog. So many great information laid out here!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7882528729236683983.post-83893616739166322142015-02-20T17:09:52.070-08:002015-02-20T17:09:52.070-08:00*I meant to say "...that weakened "herd ...*I meant to say "...that weakened "herd immunity" is *not* 'real.'"Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7882528729236683983.post-65280463782968297812015-02-20T17:07:01.288-08:002015-02-20T17:07:01.288-08:00Hi Matthew, I have a couple questions about herd i...Hi Matthew, I have a couple questions about herd immunity. I'll start by letting you know where my bias is - I'm pro-vaccine, so not surprising I've been having conversations with anti-vax folks who have directed me to rather bias articles stating that either 1) herd immunity "does not apply" to vaccines or 2) that the logic behind herd immunity is flawed because the vaccines we receive as children wear off after some amount of time and most adults never go back to get vaccinated again, except maybe if they step on a nail, yearly flu shots, or travel outside the country. (Here is an example of one such article that I felt likely to be anti-vax biased - http://www.vaccinationcouncil.org/2012/02/18/the-deadly-impossibility-of-herd-immunity-through-vaccination-by-dr-russell-blaylock/) So, what is the kernel of truth (is there one?) that these statements are based on? Do vaccines wear off and should adults redo vaccinations on a similar schedule as their children after a certain age? When calculations are done, in the case of measles, for example, that X state (say, California) is close to or going over their 5% of unvaccinated that weakens herd immunity, are adults who may not have been vaccinated since the were children included in the 5% or the 95%? Or is it, perhaps, that by the time of adulthood, those who were vaccinated as children are less likely to catch measles anyway because they are over the age of greatest risk, assuming they have no auto-immune issues, and that keeps herd immunity intact? You can probably tell by my question that I only have a high level understanding of herd immunity and am not, at this point, able to intelligently refute the idea that weakened "herd immunity" is something "real."Anonymousnoreply@blogger.com