Latest on Immunization during Pregnancy

We are all hopeful that this flu season may at last be winding down a bit.  Note that public health authorities recommend that, if you haven’t yet received a flu vaccine, it is still recommended to get one now.  I want to briefly mention vaccination for a particularly important and vulnerable population of people–pregnant women.  It’s relevant not only for this flu season but for those women who may become pregnant in the coming months and will be waiting to deliver as we enter flu season 2018-19.

A new study looked at over 400,000 infants born from 2004-14 who’s pregnant mothers were immunized against flu or with Tdap (against pertussis–“whooping cough”).  The study found no increased risk in those infants for hospitalization or death in the 1st 6 months of life.  The researchers reported that this is good news on top of previous similar reports that found Tdap or flu vaccine during pregnancy carried no increased risk to the baby for neonatal death, NICU admission, infections, respiratory, or neurologic complications, nor did it compromise infant growth out to 7 months and development out to 13 months.

They also noted significant benefits to the baby.  Maternal anti-flu antibodies crossed the placenta and provided good protection to the baby during the 1st 6 months.  Flu vaccine is not available <6 months, so this maternal transplacental transfer is all the antibody protection that these young babies can get.  They found that maternal Tdap during pregnancy lowered subsequent respiratory hospitalizations in those newborns during their first 6 months as well.  Of importance is that this data supports previous studies that drew similar conclusions regarding both flu vaccine and Tdap for pertussis.

The best time for a pregnant woman to receive Tdap is weeks 27-36.  Flu shots should be done any time that a woman is pregnant during flu season (check with your obstetrician).  Daddies get your shots too–its likely safer for you, your wife, and your baby (again, check with your doctor).

Flu mortality is up to 5x greater during pregnancy and of similarly greater risk for infants– in 2013-14 of 96 pediatric deaths 18 were in < 6 mo olds.  A word about the previous data: flu is a real public health problem and we should take it seriously.  Nevertheless, for healthy women of child bearing years and even for little infants, death from influenza in the US is rare.  As I always stress: caution–yes, panic– NO.

To summarize: flu and Tdap vaccination for pregnant women is beneficial to the women, safe for the child AND provides important protection during baby’s first months of life.  Ask me or your doctor for more information about it.

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Flu and tamiflu

The ONLY medical story anyone is discussing currently is influenza, so let’s review quickly.  Influenza is an RNA virus(genetic material RNA not DNA) that is identified by 2 “antigens”–outer coat proteins –called hemagglutinin (H) and neuraminidase (N).  There are a dozen+ variations of both H and N found on different “strains” of the virus which mutate via 2 pathways: “antigenic drift”–small changes of only a few molecules on the protein render it unfamiliar to the immune system’s defenses; and “antigenic shift”–a more dramatic change in the chemical makeup of H, N, or both.  When that happens we may get pandemics–more extensive, serious infections. This happens periodically–1959, ’68, 2009, and the granddaddy of all flu seasons, 1919, when, worldwide, millions died.  That event remains the worst flu pandemic in modern history –still the stuff of public health workers’ nightmares.

Given the large number of different H’s and N’s, there are literally hundreds of possible flu combinations. Practically, however, we really only have a few that cause most problems–H1N1, H2N2, H3N2, H5N1, H1N2, and a few others.  These are the strains that infect humans, pigs, and domestic poultry(chickens, ducks).  It is the interplay of influenza infecting these various host species that enables these buggers to change so subtly but effectively to make us sick every year.

Vaccine is produced by growing virus in egg culture in “the off season” and then noting how the H’s and N’s change, predicting and producing  shots based on those observations. However, the virus mutates at variable and unpredictable rates, so it can still change at least a bit after vaccine is manufactured.  Most of these “escape mutations” are meaningless as they usually render the virus LESS transmissible.  But when it goes the other way the vaccine becomes less effective as it may “miss the target.”  While that occurrence is relatively infrequent, given the speed and frequency that flu mutates it still is not rare–including this year, when estimates for vaccine effectiveness are only 10-30%.

We hear a lot about tamiflu (oseltamivir), which blocks production of N.  Without N the virus cannot break out of infected cells to attack other cells, curtailing infection.  The idea is to start early enough to block virus spread across your body and shorten illness duration.  Later in the course,  “virus load” is much higher–treating after 48 hours is literally “shutting the barn door after the horse escapes.”

The evidence for tamiflu is somewhat mixed.  Lancet reported strong effect, but that was mostly on mortality in seriously ill, hospitalized people with flu.  The Cochrane Collaboration study found more limited benefit–<24 hrs symptom relief.  Side effects were infrequent–<5% GI (diarrhea, nausea, pain) and <1% psychiatric (confusion or lethargy.)  More severe psychiatric  problems were only anecdotal.

My own experience is that tamiflu is mild and safe, but also of only limited benefit.  So I feel it’s useful–especially if started <48 hours–but no miracle and certainly not essential.  Best to focus on fever control, rest, and lots of fluids.  So give me a call to discuss.

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