This is the first in a multi-part series of articles that will be published in The Vaccine Reaction containing updated information from a special report on vaccine strain virus infection, shedding and transmission originally published by NVIC in November 2014.
Part I—Can People Receiving Live Virus Vaccines Transmit Vaccine Strain Virus to Others?
Public health officials say that unvaccinated children pose a big danger to those around them and even threaten the health of fully vaccinated children and adults because vaccines can fail to prevent infection in vaccinated persons.1 2 3 4 Today, the most common argument used to justify “no exceptions” mandatory vaccination laws is that unvaccinated people pose a serious health threat to others who “cannot be vaccinated,” such as the immune-compromised.5 6
Some parents of unvaccinated children are asking the opposite question: Could my unvaccinated or immune compromised child get sick from coming in contact with a recently vaccinated person?
When it comes to live virus vaccines, the short answer is: Yes.
During a viral infection, live virus is shed in the body fluids of those who are infected for varying amounts of time and can be transmitted to others.7 8 9 Vaccine strain live virus is also shed for varying amounts of time in the body fluids of vaccinated people and can be transmitted to others.10 11 12
Although public health officials maintain that live attenuated virus vaccines rarely cause complications in the vaccinated person and that vaccine strain viral shedding rarely causes disease in close contacts of the recently vaccinated,13 it is important to be aware that vaccine strain live virus infection can sometimes cause serious complications in vaccinated persons and vaccine strain live viruses can be shed and transmitted to others with serious or even fatal consequences.
Viruses: Microbes That Help, Harm and Evolve
Unlike bacteria, viruses are microbes that that cannot multiply on their own but need a human, animal or other living host to replicate. Viruses inject their genetic material into the cells of humans and other living hosts (including plants, insects and bacteria) in order to replicate.
Many viruses have developed various molecular mechanisms to evade the immune responses of their host. There is great diversity among viruses and they often mutate and recombine with other viruses while continually being shed and transmitted in body fluids and waste products of animals and humans.14
There is an ongoing debate among scientists about where viruses came from and how they evolved and are still evolving.15 One virologist observed that replicating and mutating viruses are the “world’s leading source of genetic innovation:”
The huge population of viruses, combined with their rapid rates of replication and mutation, makes them the world’s leading source of genetic innovation: they constantly ‘invent’ new genes. And unique genes of viral origin may travel, finding their way into other organisms and contributing to evolutionary change.16
Discussing the co-evolution of viruses with humans and other living organisms, another virologist wrote in 2012 that during epidemics viruses evolve. Genetic and environmental co-factors make some individuals more or less likely to die from or survive the infection, producing an increase of the numbers of resistant individuals in the population:
Viruses can become particularly dangerous when they evolve to acquire the possibility to infect new animal species. The defense systems of the new host may be generally unable to counteract the new pathogen and many individuals will die. In any epidemic, there are also individuals showing little sensitivity to or complete resistance to the particular pathogen. Both increased sensitivity and resistance to the infection are specified by the individual’s genetic makeup and various environmental factors. Accordingly, mass epidemics not only produce new virus variants but also alter the host population structure: highly sensitive individuals die, while the portion of resistant individuals in the population increases. Therefore, the coevolution of the virus and the host is a mutually dependent process.17
Viral Infections Both Trigger and Are Protective Against Autoimmunity
Most people fear and view viruses as dangerous microbes that only cause sickness and death. However, emerging evidence has revealed that viruses play an integral role in helping us stay well, too.18
Healthy infants experience many different kinds of wild-type viral infections and shed virus without showing any clinical symptoms of illness. In addition to the protection they receive from maternal antibodies, viruses help the infant’s immune system develop and gives them early protection against more serious viral infections in infancy and later in life.19 20 21
Depending upon individual genetic variability, viral infections have been associated with the triggering of autoimmune disorders like type 1 diabetes in some individuals; however, for many other people viral infections appear to be protective against development of autoimmunity.22
Public Health Policies & the Hygiene Hypothesis: According to scientists discussing the ‘hygiene hypothesis,’ increased sanitation and public health interventions in modern societies have reduced the diversity of early experiences with viral and bacterial infections among infants and children and one negative outcome has been an increase in autoimmune and allergic diseases.23 They suggest that some infectious microbes, especially those that have co-evolved with humans, protect against a wide spectrum of immune-related disorders.24 25
The next article in this TVR series will be The Human Microbiome: Viruses R Us.
1 Aleccia J. In Texas and beyond, hot spots for vaccine refusers alarm officials. NBC News Aug. 31, 2013.
2 U.S. Department of Health and Human Services. FDA study helps provide an understanding of rising rates of whooping cough and response to vaccination. FDA Press Release Nov. 27, 2013.
3 Fox M. Flu Shot Fail: Why Doesn’t the Vaccine Always Work? NBC News Feb. 8, 2014.
4 Marder J. You Could Get Measles Even If You’re Vaccinated. PBS Jan. 28, 2015.
5 Vela V. Vaccination bill should sting a bit less. Colorado Community Media April 23, 2014.
6 Dell’Antonia KJ. Want More Kids Vaccinated? End Religious and Personal Exemptions. The New York Times Feb. 2, 2015.
7 Baron S, Fons M, Albrecht T. Viral Pathogenesis. In: Medical Microbiology, 4th Edition. University of Texas Medical Branch at Galveston 1996.
8 Schwartz RA. Enteroviruses. Medscape Sept. 11, 2014.
9 National Vaccine Information Center (NVIC). Ebola (Ebola Hemorrhagic Fever). NVIC.org.
10 King JC, Treanor J, Fast PE et al. Comparison of the Safety, Vaccine Virus Shedding and Immunogenicity of Influenza Virus Vaccine, Trivalent, Types A and B, Live Cold-Adapted, Administered to Human Immunodeficiency Virus (HIV)-Infected and Non-HIV Infected Adults. J Infect Dis 2000; 181(2): 725-728.
11 Payne DC, Edwards KM, Bowen MD et al. Sibling Transmission of Vaccine-Derived Rotavirus (RotaTeq) Associated with Rotavirus Gastroenteritis. Pediatrics 2010; 125(2).
12 McKenna M. Polio vaccination may continue after wild virus fades. CIDRAP Oct. 16, 2008.
13 Mallory RM, Yi T, Ambrose CS. Shedding of Ann Arbor Strain live attenuated influenza vaccine virus in children 6-59 months of age. Vaccine 2011; 29(26): 4322-4327.
14 Fleischmann WR. Viral Genetics. In: Medical Microbiology, 4th Edition. University of Texas Medical Branch at Galveston 1996.
15 Wessner DR. The Origins of Viruses. Nature Education 2010; 3(9): 37.
16 Villarreal LP. Are Viruses Alive? Scientific American December 2004.
17 Shchelkunov SN. Orthopoxvirus Genes That Media Disease Virulence and Host Tropism. Adv Virol 2012.
18 Pullen LC. Bacterial Microbiome Move Over: the Gut Virome Makes Its Debut. Medscape Nov. 19, 2014.
19 Kapuskinsky B, Minor P, Delwart E. Nearly Constant Shedding of Diverse Enteric Viruses by Two Healthy Infants. J Clin Microbiol 2012; 50(11): 3427-3434.
20 Sahehaju K, Knip M, Virtanen SM. Maternal Antibodies in Breast Milk Protect the Child from Enterovirus Infections. Pediatrics 2007; 119(5): 941-946.
21 Navarini AA, Krzyzowska M, Lang KS et al. Long lasting immunity by early infection of maternal-antibody-protected infants. Eur J Immunol 2010; 40: 113-116.
22 Boettler T, von Herrath M. Protection against or triggering type 1 diabetes? Different roles for viral infections. Exper Clin Rev Immunol 2011; 7(1): 45-53.
23 Salur L, Oikarinen S, Tauriainen S et al. Enterovirus infections in young infants: Are children still protect by maternal antibodies? Human Vaccines 2011; 7(9):966-971.
24 Okada H, Kuhn C, Feillet H, Bach JF. The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update. Clin Exp Immunol 2010; 160 (1): 1-9.
25 Vieira SM, Pegovich OE, Kriegel MA. Diet, Microbiota and Autoimmune Disease. Lupus 2014; 23(6): 518-526.