This is a guest post by Kimberly Mulligan, PhD from the department of biological sciences at California State
University Sacramento
Hi parents! Scientist here. I decided to write a long post
about vaccines to help shed some light on how vaccines work and, hopefully,
bring some clarity to topics of debate. The amount of misinformation about
vaccines feels a little out of control to me. And no matter what you think
about vaccines, it’s tough to wade through this information without a
scientific background. FYI, my science background: PhD in developmental biology
from Stanford University, postdoctoral research at UCSF on the molecular basis
of brain development with an emphasis on a group of genes implicated in autism
and other neuropsychiatric disorders, and I just joined the faculty at CSUS
this January where I teach molecular cell biology and will have a research
program focused on the molecular basis of neurodevelopment and neuropsychiatric
illness. Ok, on to the fun stuff. (It’s
long because I wanted to be comprehensive and address all of the questions I
usually get about vaccines.)
First, I ask that you read this with an open mind. Having an open mind is an integral quality of
good scientists – it is the only way to objectively analyze data. (Open minds are
wise minds!) I also want to add that this debate gets nasty, but in the end we
all love our kids and want what’s best for them (as a mama of two, I get
that). I am not judging, I do not feel
that is my place as a scientist – my place as a scientist is to arm you with
information and help you better understand that information.
Important vocabulary: pathogen = disease-causing bacteria or
virus
Q: Ok, so what are
vaccines? (I feel like this very basic question is often not clearly
answered.)
A: Usually they
are viruses or bacteria that have been modified so they cannot hurt you, but
still look like pathogens to your immune system. That part is key. When a weakened
pathogen (or “acelluar” pieces of a pathogen) enters your body your immune
system responds by making antibodies that will bind specifically to that
pathogen, and target it for destruction. Here’s the really cool part – our
immune system makes cells called memory B cells that will stay in our body for
a really long time (depending on how strong the vaccine is). These memory B
cells are primed to make antibodies specific for that pathogen if you were to
get infected again. This is important because our immune response can take a
long time - long enough for pathogens to have debilitating and sometimes lethal
consequences. If you have those B cells ready to go, your body makes specific
antibodies that will get rid of the pathogen before it hurts you.
Q: What about the
other scary sounding stuff in vaccines?
A: They are all
there to make sure the vaccine stays safe and effective. And while they sound awful,
they are all actually totally safe in the amounts present. For example,
formaldehyde sounds scary, but did you know that it is a normal metabolic
byproduct that your body produces in small amounts constantly? You produce more
formaldehyde over a matter of minutes than you get from a vaccine. Another fun
fact: there is 4-15 times more formaldehyde in a single apple than any one
vaccine. And your body simply processes it and gets rid of it (again, it knows
how since you are always producing it). Aluminum? Present in things ranging from organic pears
to natural breast milk. One of the first things biochemistry students learn is
that dose matters. Yes, large amounts of aluminum and formaldehyde are bad…but
large amounts of water can be lethal. Oh, and mercury-containing thimerosol is
no longer in early childhood vaccines because it was removed due to public
outcry. However, there is still zero scientific data to suggest that thimerosol
has any detrimental effects. In fact, the type of mercury in thimerosol is
ethyl mercury, which is readily flushed from the body. The bad mercury that our
body has a harder time getting rid of is methyl mercury (found in tuna).
Q: Why should you
trust a big pharma who profits from vaccines?
A: My first
answer is that you don't have to. There are a lot of scientists who have
published research on the safety of vaccines that are not affiliated with big
pharma and do not profit from the results of their findings. They are people
like me – who became scientists because they wanted to help learn more about
biology in order to diminish human suffering. We work for academic
institutions, not big pharma. We ask questions without a vested interest in the
answers. These are the scientists that can provide you with unbiased
information. You can do a search for yourself on the largest database of
scientific journals here:
http://www.ncbi.nlm.nih.gov/pubmed
You will find that when you search for studies on autism and
vaccines, of the hundreds of studies conducted, there is still no scientific
data to suggest a link between the two. For example, every epidemiological
study conducted on populations of children living in the same community has
shown autism occurs at the same rate in vaccinated and unvaccinated children.
Q. What is currently
thought to be the cause of autism?
A: It is
currently thought that autism is a neurodevelopmental disorder that often begins
in utero. A number of the autism risk
genes identified affect how the brain develops during gestation. There were
actually a couple of papers very recently published indicating specific
mutations in a large number of candidate risk genes for autism1, 2.
There has also been research showing the influence of environmental factors
like maternal antibodies that are present in the womb, which were identified by
scientists at the UC Davis MIND Institute3. Autism is a very
complicated disorder, and we certainly don’t have all of the answers! But,
again, there has been an overwhelming amount of time and money dedicated to
investigating a potential link between autism and vaccines, and every study has
come back with the same results: there is no data to suggest a link between
autism and vaccines.
Q: Back to the
big-pharma-makes-a-lot-of-money-argument.
A: Yes, they do. They
make money on every drug they produce. I have opinions on big pharma’s business
practices that I won’t go into now because it actually has nothing to do with
the argument about vaccine effectiveness or safety. For better or for worse,
our entire medical system is profit based (our entire economy is, actually). The
people at the forefront of the anti-vaccination movement also make a lot of
money. That is not why I don’t believe them, though. I don’t believe
anti-vaccination proponents because of the absence of scientific data to
support their claims. As a scientist, I only believe what the scientific data supports.
I read research, not opinions. (That is not meant as a slight to anyone! I am simply stating my practices. I know that
reading primary research papers can be like reading a different language if you
do not have a science background, so I would not really expect any
non-scientist to have this practice. It’s the same reason I don’t read
economics papers. Bleh!)
Q: What about
vaccine-related injury?
A: The overall
risk is something like 0.003%. And the VAST majority of those 0.003% have minor
allergic reactions. Severe allergic reactions can occur, though they are
extremely rare. There have been a few cases of autoimmune disorders being
triggered by a vaccine. It is not entirely clear whether the vaccine was
actually the trigger because it could have been triggered by any pathogen. Importantly,
people who are immunocompromised, meaning they have a weakened immune system (chemotherapy
patients, HIV patients, genetic immune deficiencies, etc.), cannot be immunized
because their immune systems are so weak that even the weakened virus might
hurt them. All of these people fall into the class of people who should not get
vaccinated and for whom herd immunity is so important!
Q: What is herd immunity?
A: It’s kind of
basic math. Viruses cannot replicate on their own. They need to infect a host
cell in order to replicate. If they don’t make it into a host cell, they will
eventually die. Here's an easy example: a person infected with a virus walks
into a room where there are 20 vaccinated people separating him from a single
unvaccinated person. That virus cannot move from the infected person and replicate
in any of the vaccinated people because once it gets into their bodies, those
memory B cells start pumping out antibodies that kill it before it can
replicate and spread. Therefore, those 20 vaccinated people make it harder for
the virus to make it to the single unvaccinated person. If half of the people
were unvaccinated, that virus would get to have a replication party in all of
their cells and would have a much easier time surviving, multiplying, and spreading.
Herd immunity is just a basic principle about how infectious pathogens spread. If
someone tells you it doesn’t exist, you should be wary of any other scientific
information they give you because it means that they have never taken or
studied immunology or microbiology and are not qualified to have an educated
discussion about those topics.
The tricky thing about vaccines and herd immunity is that herd
immunity really only works when a high percentage of the population are
vaccinated. If not, then viruses have an easier time spreading around our
communities, putting at risk our neighbors who cannot be vaccinated (newborns,
cancer patients, etc.), and who are also much more likely to die as a result of
infection. That is why the scientific community is so scared. We feel that even a single death from a
vaccine-preventable disease is a tragedy.
Q: Isn’t natural
immunity better than vaccine-induced immunity?
A: Well, the
immune response is stronger because the pathogens are not weakened, so if you
make it through the illness you will, in theory, have a great supply of those
memory B cells. The problem is that a lot of these vaccine-preventable
pathogens can cause blindness, deafness, brain damage, paralysis, or death. I
know of a mama who has a sister who contracted rubella while she was pregnant. Her
baby was born blind and deaf because of the infection. So, yes, she now has
great immunity to rubella. But she would give anything to have had
vaccine-induced immunity prior to her pregnancy.
Q: Why do some
vaccines not give lasting immunity?
A: Each vaccine
has a varying degree of effectiveness. By effectiveness I specifically mean the
quantity and quality of memory cells that will stick around in the immune system
post-vaccine. For example, the smallpox vaccine gave immunity for 65 years
whereas the pertussis vaccine only lasts for about 10 years. This is the
purpose of boosters. Boosters essentially tell your immune system that it is
still important to mount a defense against the pathogen, and replenishes your
stock of memory cells.
Q: I heard a lot of
adults are to blame for the current measles outbreak. Should adults get
vaccinated, too?
A. Absolutely! If
you are unsure of your immunity, you can talk to your medical provider about
checking your titer (a measure of your immunity), or you can just get a
booster. Even if you’ve had a booster, but can’t exactly remember when and your
provider doesn’t do the titer test, getting another booster cannot hurt you.
Q: Why do babies
often get fevers after being vaccinated?
A: Part of the
natural immune response is the release of molecules called chemokines, which
cause fever. As a mama, I know how scary it can be when your little one has a
fever, but a post-vaccine fever is indicative of a robust immune response and
means they are making great memory B cells. That does not mean you shouldn’t
treat your baby’s fever! (Please consult
your pediatrician on when you should treat your baby’s fever.)
Q: What’s up with
vaccine shedding?
A: Vaccine shedding is something
only possible with a live attenuated virus. This is different from the
pertussis vaccine, for example, which is an acellular vaccine, meaning it
contains various pieces of the pertussis bacterial molecules and is not
infectious at all, cannot cause illness ever, and cannot shed. Again, a live
attenuated virus is a weakened virus that reproduces so slowly that a normal
immune system will take care of it before it causes any harm. If a person is
immunocompromised, live attenuated vaccines cannot be used because their immune
system might not be able to handle even a weakened virus. The nasal spray flu
vaccine does have a risk of vaccine shedding because the vaccine is
administered directly to the mucus membranes of the nose. Therefore, if that recently
immunized person were to sneeze onto an immunocompromised person, there is a
theoretical possibility that the attenuated virus could give that immunocompromised
individual the flu. This is why it is recommended to stay away from
immunocompromised individuals for a week after getting the nasal spray flu
vaccine. Other live attenuated viruses
are injected into muscle. Some of the weakened virus will get into the
lymphatic system, which is where all that good immunity will happen (production
of specific antibodies, effector cells, and memory cells that will stay around
for a long time). From there, some of the vaccine can enter saliva and mucus,
although it is going to be a much lower amount. I think this is why the CDC
only has the recommendation to steer clear of immunocompromised individuals in
the case of the nasal spray flu vaccine. BUT, and this is critical, the virus
that would potentially be shed post-vaccine is the attenuated (weakened) virus
that does not cause illness in a person with a normal immune system. This is
why vaccine shedding does not cause disease EVER in a person with a normal
immune system. It would essentially be like getting an ultra-tiny dose of a
vaccine (not enough to even cause an appreciable immune response that would
lead to acquired immunity). This is anecdotal, but when my daughter was
newborn, my husband did not realize this about the nasal spray flu vaccine when
he took our 2 year-old to the doctor…and he got him the nasal spray form of the
flu vaccine. I’m happy to report that my newborn daughter did not get the flu.
I actually wasn’t really worried; it’s a very minimal risk….but when a person
is severely immunocompromised it is important to worry about any potential risk.
Q: If I have a baby
that is too young for MMR, could a booster given to a breastfeeding mama give
the baby passive immunity through antibodies present in the breast milk?
A: Passive
immunity is the transfer of active antibodies from one person to another. This
happens during pregnancy when antibodies present in mama cross the placenta to
the developing fetus. I recently spoke to an immunologist friend about passive
immunity through breast milk. I myself was considering getting the MMR booster
to help my 7 month-old baby girl, but he said (sadly) it probably would not
boost her passive immunity an appreciable amount (for a virus as strong as
measles, anyway). There are five classes of antibodies (IgA, IgG, IgD, IgE, and
IgM). The type that is most effective in preventing infection from something
like the measles is IgG. These antibodies cross the placenta during pregnancy
and give passive immunity to the baby when it is newborn. The primary type of
antibody that gets into breast milk is IgA. It provides some protection, but
it’s just not as great as IgG.
Q: If newborns
get passive immunity from mama during pregnancy, why are they susceptible to
illness?
A:
Passive immunity only lasts for a short time. That’s because antibodies tend to
not survive very long (a few weeks to a few months, on average). Unfortunately,
the effector cells and memory cells that are responsible for making the
antibodies in mama do not cross the placenta. The memory cells are the cell
types that stick around for years to provide lasting immunity. I read a study
that indicated 88 percent of babies of vaccinated mothers have passive immunity
to measles at 4 months, and that number dropped to 15 percent by 8 months of
age4. Although, and this is important, the amount of antibodies
acquired through passive immunity may not be sufficient to protect the baby
from a strong pathogen.
Q: What about
the alternative vaccine schedule versus the CDC recommended vaccine schedule?
A: I've
never found evidence to support the alternative vaccine schedule. It is my
understanding that it is something to make parents feel more comfortable. There
are a lot of factors taken into account for the CDC schedule, which have to do
with considerations like when the acquired immunity will be best. For example,
MMR is not given until 12 months because they want to make sure that all
passive immunity acquired from mama during pregnancy is gone by the time the
vaccine is administered because those circulating antibodies would decrease the
immune response to the vaccine. So MMR can be given at 6 months, but is better
at 12 months...and I recently read a study indicating even a little tiny bit better
at 15 months5; but, you could possibly do the initial shot earlier
than 12 months and then get the booster early if you are concerned about
measles in your community (of course, talk to your doc about these decisions).
I hope this was helpful! Again, I have no financial interest
in this debate. As the mama of a 7 month-old baby girl who is not old enough to
have MMR, a 2 year-old little boy who only now has partial immunity, and as the
stepdaughter to a wonderful man who spent his final 9 months severely
immunocompromised due to chemotherapy, I am certainly emotionally invested in
the debate. But as a scientist who has read thousands of pages of scientific
research, I only want to help spread knowledge and quell fear.
For links to more information about vaccines please check out this post: http://mommedicine.blogspot.com/2013/03/immunization-information.html
References
1 Iossifov I, et al., The contributions of de novo
coding mutations to autism spectrum disorder. Nature. (2014) 515(7526)
2 De Rubeis S, et al., Synaptic, transcriptional
and chromatin genes in autism. Nature. (2014) 515(7526)
3 Bauman MD, et al., Maternal antibodies from mothers of children with autism
alter brain growth and social behavior development in the rhesus monkey. Transl
Psychiatry. (2013) 9;3
4 De Serres, et al., Passive
immunity against measles during the first 8 months of life of infants born to
vaccinated mother or to mothers who sustained measles. Vaccine. (1997) 15(6-7):620-3.
5 Hinman A., et al., Comparison of Vaccination
with Measles-Mumps-Rubella Vaccine at 9, 12, and 15 Months of Age. J Infect Dis.
(2004) 189
