Polio vaccination coverage and seroprevalence of poliovirus antibodies after the introduction of inactivated poliovirus vaccines for routine immunization in Japan.

In Japan, the oral poliovirus vaccine (OPV) was changed to 2 types of inactivated poliovirus vaccine (IPV), the standalone conventional IPV (cIPV) and the Sabin-derived IPV combined with diphtheria-tetanus-acellular pertussis vaccine (DTaP-sIPV), for routine immunization in 2012. We evaluated polio vaccination coverage and the seroprevalence of poliovirus antibodies using data from the National Epidemiological Surveillance of Vaccine-Preventable Diseases (NESVPD) from 2011 to 2015. Several years before the introduction of IPV in 2012, OPV administration for children was refused by some parents because of concerns about the risk of vaccine-associated paralytic poliomyelitis. Consequently, in children aged <1 years who were surveyed in 2011-2012, polio vaccination coverage (45.0-48.8%) and seropositivity rates for poliovirus (type 1: 51.7-65.9%, type 2: 48.3-53.7%, and type 3: 15.0-29.3%) were decreased compared to those surveyed in 2009. However, after IPV introduction, the vaccination coverage (95.5-100%) and seropositivity rates (type 1: 93.2-96.6%, type 2: 93.1-100%, and type 3: 88.6-93.9%) increased among children aged <1 years in 2013-2015. In particular, seropositivity rates and geometric mean titers (GMTs) for poliovirus type 3 in <5-year-old children who received 4 doses of IPV (98.5% and 247.4, respectively) were significantly higher than in those who received 2 doses of OPV (72.5% and 22.9, respectively). Furthermore, in <5-year-old children who received 4 doses of either DTaP-sIPV or cIPV, the seropositivity rates and the GMTs for all 3 types of poliovirus were similarly high (96.5-100% and 170.3-368.8, respectively). Our findings from the NESVPD demonstrate that both the vaccination coverage and seropositivity rates for polio remained high in children after IPV introduction.

Shedding of Rubella Virus among Infants with Congenital Rubella Syndrome Born in Tokyo, Japan, 2013-2014.

Rubella is usually a mild illness, with febrile rash being its main symptom. However, serious consequences of rubella infection can result when the infection occurs during the early stages of pregnancy. After the occurrence of a rubella outbreak in Japan that was observed from 2012 to 2013, 45 infants were reportedly born with congenital rubella syndrome (CRS). We prospectively followed the 15 CRS cases reported in Tokyo to determine the virus shedding periods by using nested reverse transcriptase-polymerase chain reaction to detect rubella virus genes. Throast swabs were used for virus detection. The virus shedding period was measured from birth until the time when the sample last tested positive followed by 2 consecutive negative samples. Kaplan-Meier method was used to estimate the proportion of cases remaining positive for rubella virus genes over time. The proportion of CRS cases shedding virus dropped steadily after birth, dropping to 33.8% at 6 months and 16.9% at 12 months. Our findings also suggested that the earlier the mother's onset of rubella during pregnancy, the longer the infant remained positive. Based on our findings, we believe that infants with CRS should be monitored for rubella virus shedding until 1 year of age.

Interruption of the rat circadian clock by short light-dark cycles.

Ninety male Sprague-Dawley rats were exposed to 1:1-h light-dark (LD1:1) cycles for 50-90 days, and then they were released into constant darkness (DD). During LD1:1 cycles, behavioral rhythms were gradually disintegrated, and circadian rhythms of locomotor activity, drinking, and urine 6-sulfatoxymelatonin excretion were eventually abolished. After release into DD, 44 (49%) rats showed arrhythmic behavior for >10 days. Seven (8%) animals that remained arrhythmic for >50 days in DD were exposed to brief light pulses or 12:12-h light-dark cycles, and then they restored their circadian rhythms. These results indicate that the circadian clock was stopped, at least functionally, by LD1:1 cycles and was restarted by subsequent light stimulation.

Loss of circadian behavioural rhythms in rats kept in constant darkness.

Ten male Sprague-Dawley rats were exposed to 1-h light and 1-h dark (LD 1 : 1) cycles for 50 days. They were then released into constant darkness (DD) for 104 days. Exposure to LD 1 : 1 caused gradual disruption of circadian rhythms in their ambulatory and drinking activities until, finally, all the animals lost their circadian behavioural rhythms. After their release into DD, eight rats showed free-running circadian behavioural rhythms, whereas the remaining two rats showed circadian arrhythmicity for approximately 50 days in DD before they restored their free-running rhythms spontaneously.