WEBVTT - How Can Herd Immunity Help Keep a Population Safe? 0:00:01.920 --> 0:00:04.320 Welcome to brain Stuff, a production of I Heart Radio, 0:00:06.240 --> 0:00:10.680 Hey brain Stuff, Lauren vogebam Here. Keeping populations of a 0:00:10.720 --> 0:00:14.640 community free from viral disease rests in part on the 0:00:14.680 --> 0:00:19.080 success of herd immunity. Herd immunity rests on the principle 0:00:19.239 --> 0:00:22.520 of safety and numbers. If more people are immune to 0:00:22.560 --> 0:00:26.400 a certain virus, either through vaccination or through already having 0:00:26.400 --> 0:00:30.040 had the disease, then more people in the population, even 0:00:30.080 --> 0:00:33.599 if they themselves aren't immune, are protected from the disease. 0:00:34.920 --> 0:00:38.440 To illustrate this point, let's think about the bowling alleys 0:00:38.520 --> 0:00:42.239 that we're all varyingly aching to return to. Pretend this 0:00:42.280 --> 0:00:44.879 is twenty nineteen and we're packed in for hours, not 0:00:44.960 --> 0:00:47.479 a care in the world besides our frame score and 0:00:47.600 --> 0:00:51.200 access to pizza. Let's say a guy in the first 0:00:51.280 --> 0:00:55.200 lane is there despite having that season's variant of influenza, 0:00:55.600 --> 0:00:57.600 and he passes it along to a woman in the 0:00:57.640 --> 0:01:01.320 second lane. If that woman and immune to that variant 0:01:01.360 --> 0:01:04.640 of influenza, then the disease will likely continue its path 0:01:04.920 --> 0:01:07.679 lane by lane until every person in the bowling alley 0:01:07.800 --> 0:01:11.440 is infected. But if that woman is immune, then the 0:01:11.480 --> 0:01:14.640 disease could well stop with her because the virus has 0:01:14.800 --> 0:01:17.280 nowhere else to go. Assuming that the guy in our 0:01:17.319 --> 0:01:21.959 example didn't have contact with anyone else, by her immunity, 0:01:22.280 --> 0:01:25.600 she protected all the people on subsequent lanes, even if 0:01:25.600 --> 0:01:30.720 they didn't get a flu shot that year. Sounds simple, right, Well, 0:01:31.000 --> 0:01:34.840 it's not that simple. For many of us, chickenpox was 0:01:34.880 --> 0:01:38.360 a routine part of childhood, a minor annoyance but rarely 0:01:38.440 --> 0:01:42.240 life threatening. For that reason, a chickenpox vaccine was met 0:01:42.280 --> 0:01:46.800 with some skepticism when it was introduced, and still there 0:01:46.880 --> 0:01:49.840 was a push in the United States to get children vaccinated, 0:01:50.120 --> 0:01:52.760 and studies have shown that the effort had a tremendous 0:01:52.800 --> 0:01:55.760 impact on the disease and the costs associated with it, 0:01:56.280 --> 0:02:00.560 and chickenpox hospitalizations dropped by a massive scent as of 0:02:00.600 --> 0:02:05.000 twelve compared with the pre vaccine period. During the period 0:02:05.040 --> 0:02:07.600 of two thousand six to twelve, when a second dose 0:02:07.680 --> 0:02:11.919 became recommended, the hospitalization rate declined by another thirty eight percent, 0:02:12.240 --> 0:02:16.960 alleviating more costs all around. Not only does a push 0:02:17.000 --> 0:02:20.480 for a chicken pox vaccine protect child and their classmates, 0:02:20.760 --> 0:02:23.079 you can also protect grandparents who may not have had 0:02:23.200 --> 0:02:27.120 chicken pox. Protecting the elderly is also the idea behind 0:02:27.200 --> 0:02:30.160 another vaccination that many of us line up for every winter, 0:02:30.560 --> 0:02:34.160 the flu shot. Between twelve thousand and sixty one thousand 0:02:34.160 --> 0:02:38.280 Americans have died each year of the flu since of 0:02:38.400 --> 0:02:44.040 those of flu related deaths and fifty of hospitalizations are 0:02:44.080 --> 0:02:47.919 people over the age of sixty five. While the elderly 0:02:48.000 --> 0:02:51.040 are encouraged to get a flu shot, it's actually more 0:02:51.080 --> 0:02:55.400 effective if the herd around them is vaccinated, including caretakers 0:02:55.440 --> 0:03:01.720 and visitors that might include Germany grandchildren. Oh, let's consider polio. 0:03:01.880 --> 0:03:05.360 The success of the polio vaccine demonstrated the benefits of 0:03:05.440 --> 0:03:09.160 using immunization to protect a population, and her immunity can 0:03:09.160 --> 0:03:11.960 be achieved for a whole host of diseases beyond chicken 0:03:12.000 --> 0:03:16.200 pox and the flu, including measles, mumps, and smallpox. And 0:03:16.480 --> 0:03:19.880 while the term herd immunity seems to imply that the 0:03:19.960 --> 0:03:23.320 whole herd should be vaccinated, it actually means that the 0:03:23.360 --> 0:03:27.120 whole herd is protected if a certain percentage is immunized. 0:03:27.720 --> 0:03:31.240 Mathematical models can be used to determine exactly what percentage 0:03:31.240 --> 0:03:33.960 of the population needs to be vaccinated to prevent a 0:03:34.040 --> 0:03:40.160 given communicable disease. For example, if approximately of a population 0:03:40.320 --> 0:03:44.960 is vaccinated against polio, then her immunity is achieved, but 0:03:45.320 --> 0:03:50.119 measles is more contagious than polio of a population needs 0:03:50.160 --> 0:03:55.040 to be vaccinated for her immunity to be achieved. There However, 0:03:55.560 --> 0:03:59.040 just because her immunity is achieved doesn't mean it's completely 0:03:59.080 --> 0:04:03.320 fool proof. Vaccines themselves aren't a hundred percent effective, and 0:04:03.400 --> 0:04:06.960 diseases can still strike those not immune to them. In 0:04:07.000 --> 0:04:10.800 some instances, an immunization is only effective for a few years, 0:04:11.160 --> 0:04:13.360 so the protection may have worn off a majority of 0:04:13.400 --> 0:04:16.520 the herd at the time of an outbreak. The childhood 0:04:16.600 --> 0:04:19.760 vaccinations may only delay the age at which outbreaks occur. 0:04:20.480 --> 0:04:23.920 For example, if a pregnant person contracts the measles, they 0:04:24.000 --> 0:04:27.040 in their unworn baby face far more complications than a 0:04:27.120 --> 0:04:33.279 child who endures the disease. So if vaccines don't work 0:04:33.440 --> 0:04:35.719 or just put off a mass outbreak in the herd, 0:04:36.240 --> 0:04:39.159 do we even need them at all? Some people don't 0:04:39.200 --> 0:04:41.200 think a shot in the arm is worth the good 0:04:41.279 --> 0:04:46.120 of the herd. If the word vaccine strikes fear instead 0:04:46.160 --> 0:04:49.000 of hope in your heart, then you likely came of 0:04:49.040 --> 0:04:52.520 age not in a time dominated by worries about polio, 0:04:53.000 --> 0:04:55.600 but in a time when vaccines make news because of 0:04:55.640 --> 0:04:59.960 side effects ranging from mild irritation to death. The most 0:05:00.040 --> 0:05:03.440 notable example is probably the debate regarding the claim, which 0:05:03.480 --> 0:05:06.880 is not supported by any scientific studies, that an ingredient 0:05:06.960 --> 0:05:09.920 in certain childhood vaccines may have led to an increase 0:05:09.960 --> 0:05:13.479 in autism. These days, in spite of the lack of 0:05:13.480 --> 0:05:17.159 scientific evidence to support a link between vaccines and autism 0:05:17.200 --> 0:05:19.840 and the fact that the ingredient is no longer used 0:05:19.839 --> 0:05:24.000 in most childhood vaccines, some people still have serious doubts 0:05:24.040 --> 0:05:27.320 about whether it's worth protecting herd immunity at the cost 0:05:27.360 --> 0:05:32.360 of exposing children to these supposed risks. That means that 0:05:32.480 --> 0:05:35.680 levels of vaccinations have dropped, particularly in certain parts of 0:05:35.720 --> 0:05:40.000 the United States where exemption from vaccines is granted for religious, philosophical, 0:05:40.160 --> 0:05:44.640 or personal reasons. But socioeconomic factors appear to play a 0:05:44.680 --> 0:05:48.400 bigger role than religious or personal reasons for lack of vaccination. 0:05:50.040 --> 0:05:53.040 C DC summary noted that the percentage of children without 0:05:53.080 --> 0:05:56.120 any vaccines has risen to one point three percent four 0:05:56.240 --> 0:06:00.040 kids born in compared with the two one survey that 0:06:00.120 --> 0:06:03.400 found just zero point three percent of children aged nineteen 0:06:03.440 --> 0:06:07.120 to thirty five months hadn't been vaccinated at all. The 0:06:07.160 --> 0:06:10.840 summary found this was significantly more common among children who 0:06:10.839 --> 0:06:15.080 were uninsured, Medicaid ensured, or who lived in rural areas, 0:06:15.600 --> 0:06:19.400 as seventeen point two percent of unvaccinated children were uninsured, 0:06:19.400 --> 0:06:22.279 for instance, compared with just two point eight percent of 0:06:22.320 --> 0:06:26.960 all children. A study by the Health Testing Centers using 0:06:27.040 --> 0:06:31.240 CDC data found that twenty seven states had kindergarten populations 0:06:31.279 --> 0:06:37.000 with vaccination rates below state targets. As parents who forego 0:06:37.120 --> 0:06:40.520 vaccinations may believe that they can rely on herd immunity 0:06:40.600 --> 0:06:44.120 to protect their children, children who aren't immunized may be 0:06:44.240 --> 0:06:48.719 protected by the children that did get vaccinations. However, as 0:06:48.760 --> 0:06:52.400 parental fears caused vaccination rates to drop, the safety of 0:06:52.400 --> 0:06:57.039 the herd, particularly its weakest members, can become compromised. Some 0:06:57.200 --> 0:06:59.920 children aren't able to be vaccinated because of health reasons 0:07:00.080 --> 0:07:03.560 and truly need to rely on the herd for their immunity. 0:07:05.480 --> 0:07:08.320 Of course, just because science has come a long way 0:07:08.360 --> 0:07:12.200 and addressing major illnesses doesn't mean that large scale outbreaks 0:07:12.360 --> 0:07:16.400 can't happen anymore. The COVID nineteen pandemic has left healthcare 0:07:16.480 --> 0:07:20.120 experts and world leaders grappling with what the best course 0:07:20.120 --> 0:07:23.720 of action is to combat the virus for the long term. 0:07:23.920 --> 0:07:27.440 But while herd immunity is effective for some illnesses, whether 0:07:27.480 --> 0:07:30.640 it's a viable solution for COVID nineteen remains to be seen. 0:07:31.960 --> 0:07:35.280 Evidence to date suggests that herd immunity is likely not 0:07:35.440 --> 0:07:39.400 a realistic option for COVID nineteen. For example, the country 0:07:39.400 --> 0:07:42.960 of Sweden opted to shun social restrictions adopted by much 0:07:42.960 --> 0:07:45.320 of the rest of the world in favor of offering 0:07:45.360 --> 0:07:50.360 optional guidelines to citizens and relying on her immunity. Initial 0:07:50.360 --> 0:07:55.120 reports from April indicated that it hadn't worked out so well, however, 0:07:55.440 --> 0:07:58.560 with Sweden experiencing a COVID nineteen death rate of eight 0:07:58.600 --> 0:08:03.600 percent compared with na bring, Denmark fourcent, and Norway under two, 0:08:04.120 --> 0:08:06.600 both of which enacted greater restrictions from the get go. 0:08:08.400 --> 0:08:11.960 Although the research into and school of thought around COVID 0:08:12.040 --> 0:08:15.680 nineteen changes practically day by day, it stands to reason 0:08:15.760 --> 0:08:19.000 that herd immunity might never be the miracle solution that 0:08:19.080 --> 0:08:22.640 everyone's been praying for. And this is because the virus 0:08:22.640 --> 0:08:28.000 that causes COVID nineteen is probably like other coronaviruses and influenza, 0:08:28.240 --> 0:08:32.000 and that it will mutate over time. When it mutates, 0:08:32.080 --> 0:08:35.319 any antibodies from a prior infection will provide little, if 0:08:35.360 --> 0:08:39.400 any protection. So people who came down with COVID nineteen 0:08:40.559 --> 0:08:43.040 might be protected for a few months to a year 0:08:43.120 --> 0:08:49.160 or two, but lifelong immunity is decidedly unlikely. And don't 0:08:49.160 --> 0:08:52.520 forget that COVID nineteen is about ten times more deadly 0:08:52.559 --> 0:08:56.400 than the flu, and even higher among vulnerable populations like 0:08:56.559 --> 0:09:00.120 the elderly. As a result, it's important that every one 0:09:00.160 --> 0:09:03.520 who's able to receive a COVID nineteen vaccine now sign 0:09:03.600 --> 0:09:06.640 up to receive one, and why our fingers are crossed. 0:09:06.679 --> 0:09:09.800 The vaccine rollout will continue at the safest possible pace, 0:09:10.320 --> 0:09:13.640 and the other treatments will be developed soon. There's a 0:09:13.679 --> 0:09:17.880 possibility that such vaccines will become like flu vaccines, available 0:09:17.960 --> 0:09:21.440 every year to protect you and the herd from new variants. 0:09:26.720 --> 0:09:29.320 Today's episode is based on the article how does herd 0:09:29.320 --> 0:09:32.600 immunity keep a country safe from diseases? On how stuff 0:09:32.600 --> 0:09:35.880 works dot com written by Leah Hoyt and Molly Edmonds. 0:09:36.360 --> 0:09:38.720 Brain Stuff is production of I Heart Radio in partnership 0:09:38.760 --> 0:09:40.600 with how stuff works dot Com and It is produced 0:09:40.600 --> 0:09:44.040 by Tyler Klein. Four more podcasts My Heart Radio, visit 0:09:44.080 --> 0:09:46.880 the iHeart Radio app, Apple podcasts, or wherever you listen 0:09:46.920 --> 0:09:47.880 to your favorite shows.