Common infections (including respiratory and urinary infections, ear infections (otitis media), stomach upsets (gastroenteritis), conjunctivitis and thrush) were documented if prevalent at 1, 3, 6, 9, and 12 months.
Although breastfeeding is not the only reason infants are less prone to severe infection, it certainly is a factor along with differences in national healthcare standards and vaccination program availability. Note that the infants from Crete had access to a high level of care.
The study's authors conclude:
Exclusive breastfeeding helps protect infants against common infections and lessens the frequency and severity of infectious episode not only in developing countries but also in communities with adequate vaccination coverage and healthcare standards.
Almost 61% of mothers were breastfeeding at one month combined with other forms of feeding, and just fewer than 17% were doing so at six months. Exclusive breastfeeding occurred in approximately one in four, or 24.6%, of mothers at one month while 10% were doing so by month six. The bottom line is that the longer an infant was exclusively breastfed; the lower was the rate of infection period.
Six month formula free infants numbering a total of 91 children demonstrated a much lower number of infections than their fellow infants that only partially breastfed or did ingested formula substitutes alone. Aside, infections that did occur were less severe amongst exclusively breast fed children.
Interesting additions to the research found, however, that factors such as parental age and education, exposure to environmental tobacco smoke, ethnicity and number of siblings influenced the frequency of infections.
The authors of the work finalize with another variable that supports the use of exclusive breastfeeding. They note that antibodies passed on through the mother's milk, as well as nutritional and immunological factors also influence the differences between infants who are exclusively breastfed and those fed partially breast milk, formula, or a mix of both.
"Protective effect of exclusive breastfeeding against infections during infancy: a prospective study"
Fani Ladomenou, Joanna Moschandreas, Anthony Kafatos, Yiannis Tselentis, Emmanouil Galanakis
Arch Dis Child doi:10.1136/adc.2009.169912