Category Archives: Vaccines

Episode 40! Lois Privor-Dumm On Vaccine Policy & Advocacy Communication


Nina gets to do her favorite thing on the latest episode: talk about vaccines! Nina is back over at the International Vaccine Access Center with Director of Policy and Advocacy Communications Lois Privor-Dumm. Lois has been working on vaccine advocacy for decades to bring life saving vaccines (like the one to prevent meningitis) to countries all over the world.

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Special Halloween podcast! On BS…aka Science Policy of the Presidential Candidates

Nina and Kenny
Nina and Kenny

Happy Halloween! Four scientists get together on Halloween to talk about a spooky topic: the science views of the presidential candidates! The science communication show Public Health United welcomes Dr. Bill Moss (see our previous podcast together), Dr. Katherine Fenstermacher (Hopkins), and Kenny Shatzkes (Rutgers, Eagleton Fellow) to talk about their frustration while watching the debates, the lessons they’ve learned in communicating science and policy, and how scientists and policymakers need to collaborate and reach compromises to form better science policies. I cannot even count the number of laughs we all have together. Truly a fun and informative episode on science policy during this election season! FYI, the title of this special edition podcast is based on Harry Frankfurt’s NYT best selling book, “On Bullshit” which details the difference between liars and bullshitters…listen to hear what the difference is and how destructive the latter can be!

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Get In The Game: Vaccine Communication with Dr. Paul Offit


I had the pleasure of visiting my old work place and interviewing Dr. Paul Offit, vaccine communicator and researcher at Children’s Hospital of Philadelphia. What ensued was a very stimulating and often times LOL kind of conversation. I am very thrilled to share this insightful podcast with a leader of scicomm (an often extremely difficult role).

Paul Offit

Download the podcast here or access on iTunes here.

Show Links:
Paul Offit at Children’s Hospital of Philadelphia
Children’s Hospital of Philadelphia Vaccine Education Center
List of Paul Offit’s books on Amazon
Information on rotavirus vaccines
Link to Paul Offit’s free vaccine course on Coursera
Watch Nina at Ignite Baltimore speaking on vaccine communication issues
PBS/Frontline Article: The Vaccine War



Vaccine Concerns: Synthesis of Vaccine Viruses (Ingredients Part 2B) by Nina Martin

After reading Part 1 and Part 2A, you should now understand why we use medium, FBS, and antibiotics to grow cells and that it’s important to passage cells if you want to continue or expand your cell line. We also discussed fibroblast cells and how they are typically used in the lab because they are easy to grow and you can expand your cell line into multiple flasks rapidly. These concepts are absolutely vital in understanding how vaccines are made.

Let us move on to the next big concept in vaccine manufacturing: attenuation of the virus. You may have already heard the term attenuate. For example, the measles vaccine is a live, attenuated vaccine. What does this mean and how does this fit in with our ingredients list?

To attenuate means to weaken; to attenuate a virus means to weaken it. Remember that for an efficacious vaccine, we want to expose people to the germ and activate the immune system without causing illness. In the lab, scientists have figured out how to change the measles virus so it will still activate your immune response, but not actually make you sick. Here’s how:

Virus attenuation via adaptation into a new host cell. 1. Sample is taken from host. 2. Passaged through chick embryos multiple times. 3. Passaged through chicken embryo fibroblasts multiple times. 4. Attenuated virus is isolated from cells and sequenced.

Wild measles virus is well suited for human cells: once you breathe it in, measles will invade your lung (epithelial) cells, take over its machinery, and reproduce itself. A scientist name Enders first discovered that if you add measles virus to non-human host cells, like chicken egg (embryo) cells, the virus will adapt (aka mutate) to its new host. This is survival of the fittest at its best! Please note that the measles vaccine virus used in MMR is passaged in chicken embryo fibroblast cells and not in eggs.

Measles attenuation
Diagram of how measles virus was attenuated. Key: Names within the colored boxes are the names of the measles strains. 1. Measles virus was isolated from a patient with last name Edmonston. 2. The Edmonston strain was serially passaged 24 times in human kidney cells, 28 times in amnion cells, 6 times in chick embryos, and then in chicken embryo fibroblasts to create the Edmonston B strain. The current measles vaccine virus in the U.S. (Attenuvax, Merk) was made by further attenuating the Edmonston B strain 40 times in chicken embryo fibroblasts. We call this live, further attenuated virus the Moraten or Edmonston-Enders strain.  The Schwarz strain, made by attenuating the Edmonston A strain, is widely used in vaccines in Europe and other countries around the world.

 By repeating the process of adding virus to cells, letting it grow, then isolating the virus and adding it to a new plate of cells, over time you can create a virus that is so well adapted to surviving in its chicken host that it can no longer efficiently reproduce in the human host. We call this process passaging the virus in cells or tissues. Please read our previous article for a nice summary of how we passage cells in the lab. The measles vaccine virus is passaged in chicken embryo fibroblasts while other vaccine viruses, like rubella, is passaged in other host cells like monkey kidneys or human diploid cells (more on this in a bit). Theoretically any cell that is not the typical cell for measles invasion could work–though some viruses will not grow at all in certain hosts. It’s important to know that we passage the virus at least 40  times (or even more depending on the specific vaccine) in chicken embryo cells. This is necessary (and great) because when you give the attenuated (weakened) virus back to the human host, there is only an extremely small chance of it reverting back to the wild virus—each round of passaging created a new batch of mutations that helped the virus survive in the chicken. It is almost impossible for the virus to jump back to the human-disease causing form.

Rubella attenuation
The rubella virus vaccine strain currently used in the U.S. in the MMR vaccine (Meruvax II) was created by serially passaging rubella virus in WI-38 cells at a low temperature (for viruses). Growing the virus in the diploid cells at low temperature resulted in the production of the avirulent (attenuated) strain RA 27/3.  Two other strains were previously used in vaccines in the 1960’s and 70’s (HPV-77 & HPV-77/DEC but were continued due to side effects and because they didn’t provide as much protection as the RA 27/3 strain did.

 So now when you see non-human cells listed in the vaccine package insert, you know why: wild virus is passaged in non-human cells many times, forcing it to adapt to the new host and no longer causing disease in the human host.

Common concern: Use of chicken embryo fibroblasts to passage virus Some people have legitimate concerns about vaccines that are prepared in chicken embryos. After isolating the virus from the egg, there still could be a small amount of chicken proteins that some people have an allergic reaction to (i.e. when you get redness and other symptoms from the flu shot). Viruses that are grown in chicken fibroblast cells (not in the egg, just in cells) do not experience an allergic reaction because the virus was never in the whole egg. So even though the measles vaccine is grown in chicken fibroblast cells, there is no reported evidence of having an egg allergy to this. Another concern is the use of chicken embryos in general. Often when people hear the word embryo, they do not realize that we mean a chicken egg. So if you don’t have an issue with eating chicken or egg products, there should also be no issue with this process. However, some people are ethically against the use and/or consumption of animals, period, and thus this is a legit concern to have. Unfortunately, we don’t have a better way to mass produce the amount of virus needed for vaccines and other research purposes. Some researchers are currently working on genetically engineering attenuated viruses and others are working on alternatives to animal testing. But these standard practices are currently the most reliable tools we have.

Common concern: Use of human fetal diploid cell lines to passage virus Let’s get some definitions out of the way. You may see the term ‘human diploid cells’. Diploid refers to the number of copies of chromosomes found in a cell (di = two). If you remember from science class, most cells of the body, besides your sex cells, are diploid. So nothing out of the ordinary there. Second, I’ve observed online that some people are confused about the term “cell line.” A cell line is a cell culture developed from a single cell and therefore consisting of cells with more or less identical genetic makeup. You can propagate some cell lines indefinitely. This is important to understand because we can isolate cells from a tissue once and then culture them for decades–we don’t isolate cells from new tissues over and over again. There are two cell lines that were first created in the 1960’s that are used to make some vaccine viruses and were originally derived from two human fetuses called Wi-38 and MRC-5. Both the Wi-38 and MRC-5 cell lines are composed of fibroblast cells from lung tissue. I’ve observed some confusion online regarding the synthesis of these cell lines: some people think fetuses are sacrificed every time this cell line is used. It’s important to understand that this cell line was made in the 1960’s from two fetuses that were already destined for abortion. The parents agreed to donate the fetuses for research at the time of termination. Others are concerned about the religious implications of using fetus cells in vaccines. First, some people are under the impression that you can find fetus cells in the final vaccine product. This is not true: the virus is isolated from the cells and washed several times. Second, the Vatican has issued a statement several years ago that is it acceptable to use vaccines that were prepared with these cells as it serves for the greater good. They also ask for better methods of vaccine manufacturing that will avoid using these cell lines. Asking for better methods is definitely a great suggestion, just remember that you need to support science funding in order for that to happen! Please read this article for more information about the cell lines used and the religious implications.

Common concern: vaccines contain cells (whether they be human, animal, other)
Please note that viruses are removed and purified from cells before vaccine manufacturing. You will see on some package inserts that residual amounts of cellular products MAY be found in the final product. I am personally not concerned about this after reading Plotkin’s article here and knowing that we consume plant and animal cells at a much larger rate than the miniscule amount found in vaccines. The vaccine product is also extensively tested and scanned for any dangerous contaminants before release.

If you read the previous articles, I hope you can see that production of the vaccine virus is separate from production of the final vaccine product that is injected into you. This means that the ingredients we have discussed so far, including animal and human cell lines, are not found in the final product (except possibly in amounts less than 1 ppm).  In the next article, we will get into how the vaccine virus is packaged into the vaccine product and what ingredients are actually found in the injectable form.

Photo credits:
Figure 1. Virus Attenuation. Taken from:
“Attenuation of measles strain” diagram modified from Plotkin et al. “Vaccines.” (textbook). Philadelphia: Saunders; 2012.

Plotkin et al. “Vaccines.” (textbook). Philadelphia: Saunders; 2012.
Plotkin. “The history of Rubella and Rubella vaccination leading to elimination.” Clin Infect Dis. (2006) 43 (Supplement 3): S164-S168.
Hilleman et al. “Live, Attenuated Rubella-Virus Vaccine.” N Engl J Med 1968; 279:300-303

Please let me know if you spot any inaccuracies in this text at

Vaccine Concerns: Ingredients Part 2a by Nina Martin

Before we get to our next big ingredient topic (how to attenuate a virus for use in a vaccine and the reagents needed to do this), we need to go over a basic lab technique : passaging cells. In the last article, we talked about cell culturing and how to grow cells in the lab. We talked about the reagents needed for this process:
-Media: nutritious liquid that contains water, sugar, salt, amino acids
to prevent contamination with bacteria
serum provides growth factors needed for cells to divide and not perish

So we have our cells in a flask with these reagents and they are growing. What do we do now? If we want to rapidly grow many cells or if we just want to maintain the one flask,  we must passage (“split”) the cells. Here’s how we passage cells: first, we start with one flask of cells, let the cells grow to a certain density (too dense and the cells will die), remove the cells from the flask, dilute them (see below diagram), and then split them into several new flasks (or just one if you want to just maintain your line). You can keep repeating this process to quickly expand your cell line. Note that we must dilute and expand cells into multiple flasks because if they get too dense in one flask, the cells will die. This is also why fibroblast cells  are often used in experiments and vaccine production: they are easy to grow and can be rapidly expanded.Slide1


Photo credits:
Passaging cells in hood taken from (video):
Fibroblast microscope image:
Flask image:


Vaccine Concerns: Ingredients Part 1 by Nina Martin


petri dish
Cells in growth medium in petri dish
Cultured cells in a flask

Vaccine ingredients can seem strange to the non-scientist because making the vaccine first requires common laboratory procedures and chemicals (aka reagents) that you may have never heard of before. I’ve observed many concerns and misunderstandings online that originate from a lack of understanding of these preliminary steps to making, for example, vaccine viruses—like the one used in the measles component of the MMR vaccine.


Measles is an example of a virus and we can think of viruses as obligate parasites: they must invade a cell in order to survive. They use the machinery of their host (i.e. human lung cells in the case of measles) to reproduce themselves and to be able to infect a new host. This means that in order for us to make the virus used in the vaccine, we must grow viruses in cells in the lab (or later on at a factory for mass production). Unfortunately, for the infant vaccines that are currently approved by the FDA, you cannot simply engineer a virus without cells (though this is a current line of research and trial). So, if you want to understand the components of our commonly used vaccines, you first have to learn a bit about how we grow cells in the lab and the reagents we commonly use to do this.


Scientist culturing cells in sterile conditions in a hood

We call the practice of growing cells in a petri dish “cell culture” or “tissue culture.” Culture = grow. In order for cells to be cultured, you have to grow them in liquids that are packed with nutrients. We call this the growth medium (it’s the pink liquid in the photos to the right). Growth media (plural of medium) is packed with the nutrients needed for cells to grow: water, sugar (i.e. glucose), amino acids, salt, etc.

serum components 2serum componentsCells also need signals to grow, called growth factors, which will activate the cell and tell it to divide and replicate. We get growth factors from another added component to the medium: serum. Serum is a component of blood. You can isolate it by spinning blood at high speeds, separating out the different components of blood: red blood cells, white blood cells, fat, and serum (also called plasma). The growth factors in serum  is absolutely necessary to culture cells. Without serum, you will not be able to grow cells.

Most laboratories use a specific kind of serum that is optimal for growing cells in the lab: fetal bovine serum or FBS. The serum comes from a cow fetus that is specially prepared by science research companies and is extensively processed for quality control (it is imperative that the serum used in research and for vaccines is sterile). The cultured cells can tell the difference between serums from different animals/ages and will actually not grow if they don’t have the right serum. That is why FBS is used—cells readily grow in this serum while they will not grow in, for example, adult cow serum. A great explanation from Research Gate (my go to website for lab questions):
“Tissue cells are inherently suicidal and they require growth factors that not only stimulate replication but are generally required to tell the cell not to undergo apoptosis. Remember that most cells (differentiated or not) know were they are because of local tissue chemical signals; be it adhesion molecules or secreted factors. Without continued stimulus by these factors cells are hardwired to undergo apoptosis because they then sense they are growing in the wrong place (hence in oncogenesis it is not just unregulated replication but molecular mechanisms of overcoming apoptosis for invasion and ultimately metastatic spread). Fetal bovine serum is awash with hormones, paracrine, endocrine and autocrine growth factors which support cells – somewhere in this mix is likely to be a factor supporting survival of your chosen cells.”

We also commonly add antibiotics to our growth medium in order to prevent bacterial growth and contamination of our cell culture. Commonly used antibiotics are: penicillin, streptomycin, and neomycin. Adding antibiotics is really important because bacteria would rapidly grow in this nutrient packed soup (sometimes we call media soup because it’s so nutritious!) without the addition of antibiotics. If any bacteria grow in your cell culture, you have to throw the whole thing out—it’s completely ruined and can’t be recovered.

Common concern: amount of antibiotics and serum in vaccines Some people have legitimate concerns about antibiotics in vaccines. Some could be allergic to antibiotics. Some are concerned about too many antibiotics given to infants. First, the addition of antibiotics to both the cell culturing process and the final vaccine product is absolutely necessary. Most vaccines cannot be shipped from the factory and used right away: you need to be able to store them. Because of the other components necessary to keep the vaccine virus stable (i.e. sugar), there is a high risk for bacterial growth in your vaccine without the use of antibiotics.

It is also important to realize that before the final vaccine product is released, the virus has to be removed from the cells and isolated for packaging into the vaccine. During this isolation process, all cell culture reagents and cells are washed away. It has been found that after this washing process, there is less than 1 part per million of fetal bovine serum and antibiotic left (think about slicing a cake into a million pieces and taking less than a slice to eat: this is a very small amount!). For the final product, 25 mg of neomycin is added, for example, to the measles vaccine. A normal dose of neomycin given to a 1 year old is ~500 mg per day to treat a bacterial diarrhea. This means that the amount found in the final vaccine is 20 times less than one normal dose of antibiotic. This is a very small amount.

Common concern: production of serum for use in vaccine virus synthesis Fetal bovine serum (FBS) is widely used in ALL cell culture practices (not just for the use of vaccines) to provide the growth factors needed for cells to survive. As I said before, older animals are not rich in the growth factors needed to survive and thus cannot be substituted for FBS.

Some people are concerned about FBS because of the way in which serum is produced. It is taken from cow fetuses. Some people are ethically against the use of animals and in particular cow fetuses. As of 2015, there is no way to make synthetic serum (think TrueBlood). The only way to get the growth factors necessary to culture cells is through this process. Down the pipeline, there may be synthetic substitutes for serum: last year promising research came out of the University of Edinburgh—the first laboratory to make real, mature red blood cells from stem cells. Reports say that this may be ready for small clinical trial by 2016. As of now, there is no feasible or reliable substitute.

Take home message: If you would like better reagents, like synthetic serum that avoids the use of animals in research, the best thing you can do is to support basic science research funding. You can do this by electing officials with a track record of supporting science. We need your support to develop better methods!


Vaccines Explained: List of Resources

In light of my vaccine podcast and Ignite talk coming up, I thought I’d share with you some great resources for vaccine information. Especially on information on what vaccines are, how they are made, and what the different ingredients are.

My go to book for general vaccine questions (please go and buy this book asap! will help you tremendously and lists sources): Vaccines & Your Child: Separating Fact From Fiction. By Dr. Paul Offit & Charlotte Moser. Amazon page here.

The rest of us: Hasn’t been updated in a while but I think the immune system and vaccine explanations are pretty good.

Skeptical Raptor: If you are having trouble understanding the vaccine package insert, you are not alone. Check out this article for a great explanation. Also a great site for general and specific information. Check out this article for links to vaccine package inserts.

Excellent resource for lists of ingredients in each vaccine at the website. It’s still hard to understand what all of the ingredients are doing from just this website, but I found it helpful to be able to find lists of ingredients. Please note: I have not read any of the other pages of the website. I can only vouch for the ingredient lists to be accurate.