Review of "Immunogenicity and persistence from different 3-dose schedules of live and inactivated polio vaccines in Chinese infants"

Introduction:

As mentioned in earlier posts, there are two approach to vaccination against polio, oral polio vaccine (OPV) and inactivated polio vaccine (IPV). However, according to Polio Eradication and Endgame Strategic Plan 2013–2018, the OPV vaccine is not as effective as IPV in preventing polio because it can lead to vaccine-derived polioviruses (VDPV). This plan mentions few countries that are still using OPV, including China. The article, Immunogenicity and persistence from different 3-dose schedules of live and inactivated polio vaccines in Chinese infants, by Lu et. al. compares the presence of immunogenicity and persistency between the oral polio vaccine and inactivated polio vaccine by testing on Chinese infants, as China is one of the nations following with OPV.

Methods:

The researchers choose Chinese infants as their subject with the permission of infants' parents or guardians. They set specific characteristics for their subjects, which include the infants being "between 60 and 89 days old on enrollment, have resided in Beijing for the previous 2 months, been born full term (≥36 weeks) with birth weight ≥2.5 kg, and have parents with the ability to follow the study protocol" (Lu et. al.). With these defined requirements, the study limited its borders to China alone. The infants were divided into four groups that differed in their vaccination schedule and type. The treatment groups were assigned as "IPV–OPV–OPV (I–O–O), IPV–IPV–OPV (I–I–O), IPV–IPV–IPV (I–I–I), and OPV–OPV–OPV (O–O–O)" (Lu et. al.) while the control only followed OPV-OPV-OPV (O-O-O) schedule, since OPV is the only vaccination method in China. The three types of poliovirus vaccine were given through IPV and OPV, depending on the treatment group. The IPV vaccine was injected into infant's thigh while OPV was administered through oral route. Blood samples were collected from 533 initial participants, however, as the research progressed, parents withdrew their children from the study and after every dose blood samples were collected from infants, including the remaining 84 that stayed throughout the entire study. The blood sample collected was stored and the serum "were tested for neutralizing antibodies for poliovirus types 1, 2, and 3" (Lu et. al.) followed by microneutralization assay, which determines the immunity. The solutions were diluted to 1:1,024 and readings greater than 1:8 were considered as positive protective level for naturalizing antibody. Further analysis were done such as use of ANOVA to compare geometric mean titer of treatment groups and chi-square to compare protective rates (Lu et. al.)

Results:

The antibody production reduced with both OPV and IPV methods of vaccination. The data for antibody production are shown below. 

The antibody titers before, one-month after vaccination and 18-months age.Lu, L., Li, X., Zhang, H., Liu, D., Zhang, Z., Wang, H., Liu, F., ... Pang, X. (February 01, 2015). Immunogenicity and persistence from different 3-dose schedules of live and inactivated polio vaccines in Chinese infants. Vaccine, 12.)

Discussion:

Through multiple test conducted by the researchers, Lu et. al., it became evident that I-I-I method was the most effective approach to vaccination as the antibody production is lower in comparison to other modes of vaccination such as the control, OPV only, or other treatments that had a mix of OPV and IPV. I believe that the researchers should expand this research to other nations and see if perhaps ethnicity or individual's race has an influence on this data reported. Also, it is important to consider the ethicality of this research as infants are used to be the subjects. Perhaps research can further carryout this experiment on other mammals that have similar response as humans to poliovirus. I suggest this because the data analysis may not demonstrate the entire population of China, where only 84 infants remained in the study and their blood antibody results are used for analysis. 

Sources:

Lu, L., Li, X., Zhang, H., Liu, D., Zhang, Z., Wang, H., Liu, F., ... Pang, X. (February 01, 2015). Immunogenicity and persistence from different 3-dose schedules of live and inactivated polio vaccines in Chinese infants. Vaccine, 12.)

Polio Eradication and Endgame Strategic Plan 2013–2018. (2013). Retrieved June 15, 2015, from http://www.polioeradication.org/Resourcelibrary/Strategyandwork.aspx