Reasons to Believe

Answering FAQs on Vaccine Safety

My previous article titled "Vaccine Safety and Loving Our Neighbors" generated some ardent reader responses. In this follow-up article I would like to acknowledge and address many of these responses, especially those from readers who expressed concern over the evidence for vaccine effectiveness and safety.

As RTB brings forward scientific evidence to support biblical faith, we desire to facilitate dialogue and have committed ourselves to pursuing truth together. It is with humility and grace that I attempt to answer the most frequently asked questions and objections concerning viruses and vaccines. (For clarity, question topics are highlighted in bold.)

What are your background and credentials for writing such an article?

In college I knew I wanted to study and research viral microbes that challenged medical science's ability to treat and prevent diseases. For the majority of 20 years, that's exactly what I did.

In grad school, I researched viruses that cause encephalitis, AIDS, and demyelination. In 1996, I completed my PhD in molecular and cellular biology (with an emphasis in virology) at the University of Pennsylvania. Subsequently, I conducted proof-of-concept (or preclinical) studies for vaccine development for viruses that cause respiratory ailments, AIDS, and other human diseases. My research focused on developing animal models and evaluating potential vaccines (and related products) to prevent and treat infections caused by human viruses.

My colleagues and I examined the best ways to generate and administer vaccines to offer the most protection with the least risk. We evaluated different routes of inoculation and different doses. We had to demonstrate the mechanism of protection for each potential vaccine and examine any potential side effects or adverse outcomes observed in the animal models.

Research of this nature is detailed and time consuming. Nevertheless, these studies must precede all clinical studies of every potential vaccine. I was involved in preclinical research for eight years at Yale University and the National Institutes of Health (NIH), two of our nation's premiere research institutes.

My motivation for writing about vaccine safety was the same motivation for my research. I believe Christians are called to steward God's creation, alleviate suffering, and pursue truth—all from a love for God and a sacrificial love for others. For me, this meant researching ways to prevent and treat virus infections. During a two-year mission trip to Russia (between research at Yale and the NIH), it also meant informing others about risks of exposure to HIV and the importance of making moral decisions. For the past decade, my Christian convictions have compelled me to continue to inform others about the scientific evidence that supports both the safety and effectiveness of vaccines.

My commitment and contribution to research and education helps alleviate human disease and suffering only when others use the knowledge and developed products to secure our public health. Christians are to care for society's most vulnerable, motivated by love, never by fear. It is, in fact, this sometimes costly love that will witness to the world that we are Christ's followers (Matthew 25:40; John 13:34; Philippians 2:3-5; 2 Timothy 1:7).

What is Dr. Ross' position on vaccine safety?

Dr. Ross reviewed and was supportive of my previous article. His primary concern was that I handle the scientific data regarding vaccination accurately—as I did.

What about the side effects of vaccines, such as injury and even death?

I, like many of you, am aware of cases where immunized individuals react aberrantly to vaccination and suffer greatly as a result. Such occurrences are extremely rare—nevertheless, every instance where an individual suffers is tragic. The direct and immediate causes for severe adverse reactions are, for the most part, unknown, unidentifiable, and unpredictable. They could be related to genetics, physiological conditions, or a rare combination of the two. The suffering seemingly triggered by vaccination is real and extraordinarily unfortunate.

Still, this suffering should not prevent a socially responsible individual's participation in life-saving vaccinations. We need to balance our emotional responses to suffering with the overwhelming evidence for vaccination's high rate of success.

The whole reason for vaccination is to avoid suffering associated with disease. It may help to remember that vaccine-preventable diseases are far more frequently associated with severe disease and death than are vaccines themselves.

Vaccines, nevertheless, are associated with real risk. Some vaccines are in fact a weakened but live virus. Since each person's physiology is different from the next's, even giving a weakened virus to someone is risky. The real question is whether the risk is reasonable. Not everyone who contracts a disease suffers severely or dies. But some do. Prior to the introduction of vaccines, many more people suffered from disease. Comparatively, the numbers of those who suffer severe side effects following vaccinations are extremely low. Furthermore, it is not unreasonable to think that those who suffer when vaccinated with a weakened live virus would, if left unvaccinated, likely suffer worse or possibly even die if exposed to the actual virus itself. Overall, for the population as a whole, the assumed risk associated with vaccination is far, far less than the assumed risk of an unvaccinated or under-vaccinated population.

How should we sort through all the conflicting information on vaccine safety?

The Internet is replete with conflicting data on vaccines. I have explained my credentials as well as my motivation in advocating immunizations. Whichever authorities we appeal to should be willing to provide the same. Many anti-vaccine commentators have no formal training or experience and are impassioned by personal anecdotes. Their data are gained second- or third-hand and manipulated in such a way as to support their agenda, which often appears fear driven.

One example of data manipulation is the claim that mortality associated with a particular disease was declining before vaccine implementation, thus this disease would have disappeared without immunization. While a decline in mortality was observed for many diseases, the conclusion is completely unsubstantiated by any data. Furthermore, it is not solely, or even primarily, death that vaccines prevent. They help us prevent deafness, blindness, paralysis, neurological disorders, pneumonia, and even spontaneous abortions. They also help protect highly vulnerable populations—the very young, very old, and very sick.

If one looks at morbidity (disease) rates over time, the continued positive impact of immunizations on mitigating disease and alleviating suffering is obvious. The conclusion supported by scientific data is that vaccines prevent suffering and save lives in the vast majority of those vaccinated and in the general population.

Is it safe to give individuals, particularly children, multiple vaccines at one time?

Vaccines are basically foreign proteins introduced into individuals artificially. All humans come into contact naturally with thousands of foreign proteins in the environment every day. God has endowed humans with amazing immune systems to handle most of these encounters of which only a fraction are associated with severe disease, and we can immunize against many of them. So although it seems like a lot of vaccines are given at once, they account for a minuscule fraction of foreign proteins we encounter naturally every day.

Do vaccines include contaminants, like mercury, animal proteins, and DNA, and how does that impact vaccine safety?

FDA representatives continually monitor the safety of vaccines and other biologics for potential contaminants such as DNA and animal proteins. Pharmaceutical companies readily comply with FDA guidelines and regulations restricting vaccine ingredients, as failure to comply can result in suspension of production and subsequent loss of income and public trust. If identified violations cannot be resolved and safety cannot be reestablished, production is halted and licensure revoked.

The FDA is so vigilant that even when there is a perceived link between an ingredient and a potential adverse effect, they restrict its use. For example, thimerosal, an ethylmercury-based preservative, was previously used in multi-use vaccines to prevent bacterial contamination. The ethylmercury killed the bacteria and was safely regulated at levels set for the far more hazardous compound, methylmercury. (Think of the difference in drinking methanol versus ethanol—the former can cause blindness, the latter a bad hangover.) Even without evidence that thimerosal was hazardous at levels found in multi-use vaccines it was removed from practically all vaccines by 2001.1

Far from being harmful, vaccines actually save millions of lives. They prevent millions of hospitalizations and millions more cases of severe disease. These are appropriate conclusions based on solid scientific evidence.

A majority of those vaccinated will experience some side effects. Most side effects are negligible. The vast majority of additional side effects are transient and not severe. Rarely, adverse, severe side effects occur that are far less serious than the debilities, disease, and risks associated with the vaccine-preventable diseases. Nevertheless these rare adverse, severe side effects do occur in a small number of individuals. Their suffering is real and tragic; but their suffering should not result in the abandonment of reason nor of a socially responsible individual's participation in life-saving vaccinations.

The current debate over vaccination is a byproduct of a privileged society where we are not usually confronted by the horrors of diseases that vaccinations have eradicated. One of the tragedies in Western Christian culture today is the idea that our rights and wellbeing are more important than others'. Too often we choose to care for others only so long as our rights are not impinged upon. Frankly, I find no model for these culturally normative attitudes in Jesus or the New Testament. I believe these attitudes model a secularized, self-oriented posture. In the Scriptures I see that we are challenged to live counter-culturally and sacrificially. As C. S. Lewis puts it, "Our charity must be a real and costly love."2 It is this love we are called to show others for the sake of Christ and for the sake of His witness to the world.

Subjects: Christian Life

Dr. Anjeanette "AJ" Roberts

Molecular biologist Anjeanette “AJ” Roberts writes and speaks about integrating science and the Christian faith. As a research scholar at Reasons to Believe, AJ is committed to seeking truth and to sharing the great news of hope found in Jesus Christ.


  1. The only exceptions in the US are multi-use influenza and meningococcal vaccines which still contain thimerosal.
  2. C. S. Lewis, The Weight of Glory (London: Society for Promoting Christian Knowledge, 1942).