I would like to begin this post with a few statistics from the CDC:
Pregnant women are twice as likely to be hospitalized if they contract influenza.
69% of reported whooping cough deaths occur in babies less than 2 month old.
Only 1 in 3 pregnant women receive the recommended influenza (flu) and whooping cough vaccines (Tdap)
These are alarming statistics and they raise some interesting ethical questions. Questions such as: Do pregnant women have a moral obligation to get immunizations during pregnancy in order to protect the health of their unborn child? Does this obligation extend to the general public?
Since 2013, ACOG has recommended all pregnant women receive the Tdap vaccine between 27 and 36 weeks gestation in order to maximize the maternal antibody response. These antibodies are then transmitted to the fetus and protect the newborn from acquiring pertussis, which causes whooping cough, until they are able to be vaccinated themselves after 2 months of age.
A recent study indicates that pregnant women who receive an influenza vaccine are 40% less likely to be hospitalized for influenza associated complications during pregnancy. In the same manner as the Tdap vaccine, maternal antibodies against influenza are passed to the fetus, resulting in protection from adverse peri- and neonatal outcomes. Infants cannot be vaccinated against influenza until the age of 6 months.
Newborns, whose mothers were not vaccinated during pregnancy, become infected through contact with unvaccinated siblings, parents, and caregivers.
Given this information and those startling statistics, it seems clear to me that any adult who will be in close contact with infants and who is physically able, ought to receive these vaccines. The ethical question is, does this ought constitute a moral obligation?
Has a pregnant women committed an ethical wrongdoing by refusing to receive vaccinations? We say that a person has a moral obligation to act in certain ways due to a relationship or agreement with another. In this case, a parent has a legal as well as moral obligation to protect the health and well-being of their child. In other circumstances, the state is legally supported by this obligation, to intervene when children are in unsafe or unhealthy situations.
Beyond the obligation of the mother, the infant also has a positive right to be protected. This is where I believe we can find the answer to our ethical dilemma. In order for the positive rights of the infant to be fulfilled, something must be done for them or provided to them. Generally speaking, the obligation to provide for the positive rights of the infant falls to the parent(s).
If parents fails to provide a safe environment for their children, it seems natural to say that they have done something morally (and legally) unacceptable. This is illustrated when states step in and remove children who are deemed to have been harmed by a parental lack of actions to protect them.
Similarly, I believe, a pregnant women commits an ethical wrong, when she fail to receive these immunizations that provide protective antibodies and aid in the prevention of life threatening infection in the infant.
The question of this obligation extending to the general public is a bit more difficult to construct such a clear argument for. Although, as a society, we have some level of agreement of moral obligations between individuals, these typically fall in the realm of negative obligations, meaning that we do not interfere with others. I suppose, if I had more time and many pages, I could argue that an unvaccinated person who is infected with influenza or pertussis, has some sort of moral obligation to protect infants who cannot themselves be vaccinated. However, I am afraid that this would be weak argument.
I prefer to conclude that rather than a moral obligation, healthy adults and children ought to receive vaccines, in order to build the herd immunity and to protect those too young or vulnerable to be vaccinated themselves.
 All statistics from the CDC found at https://www.cdc.gov/vitalsigns/maternal-vaccines/index.html photo from the CDC at https://www.cdc.gov/flu/highrisk/pregnant.htm