Poliovirus-specific memory immunity in seronegative elderly people does not protect against virus excretion.
BACKGROUND
Dutch people born between 1925 and 1945 were ineligible for vaccination with the inactivated poliovirus vaccine (IPV) introduced in 1957 and may have escaped natural infection because of reduced poliovirus circulation. We examined whether people with low or undetectable antibody levels are susceptible to infection and whether memory immunity provides protection against virus excretion.


METHODS
A total of 429 elderly participants were challenged with monovalent oral poliovirus vaccine (type 1 or 3) and followed for 8 weeks. Immune responses and virus excretion were compared for 4 groups, defined on the basis of seronegativity for poliovirus type 1 or 3, natural immunity, and IPV-induced immunity.


RESULTS
On the basis of the rapidity of the antibody response and the absence of immunoglobulin M, we saw clear evidence of memory immune responses in 33% of the participants without detectable antibodies against poliovirus type 1 and in 5% of the participants without detectable antibodies against poliovirus type 3. Fecal virus-excretion patterns were not significantly different for seronegative participants, regardless of whether they showed evidence of memory immunity.


CONCLUSIONS
Rapid antibody responses after challenge with oral polio vaccine provide evidence for poliovirus-specific memory immunity in seronegative elderly people. However, in contrast to preexisting immunity, memory immunity does not protect against virus excretion. These results have important implications for the poliomyelitis-eradication initiative, in particular for future immunization policies after eradication has been achieved.
Abbink
Frithjofna
F
Department of Infectious Disease Epidemiology, National Institute of Public Health and the Environment, Bilthoven, The Netherlands. f.abbink@rivm.nl
Buisman
Anne M
AM
Doornbos
Gerda
G
Woldman
Jan
J
Kimman
Tjeerd G
TG
Conyn-van Spaendonck
Marina A E
MA
D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood*; D005243:Feces / Q000821:virology*; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D007156:Immunologic Memory; D009426:Netherlands; D009500:Neutralization Tests; D011051:Poliomyelitis / Q000276:immunology / Q000517:prevention & control*; D017955:Poliovirus / Q000276:immunology*; D011054:Poliovirus Vaccine, Inactivated / Q000008:administration & dosage / Q000276:immunology; D011055:Poliovirus Vaccine, Oral / Q000008:administration & dosage* / Q000276:immunology; D014611:Vaccination; D017201:Virus Shedding
D000914:Antibodies, Viral; D007075:Immunoglobulin M; D011054:Poliovirus Vaccine, Inactivated; D011055:Poliovirus Vaccine, Oral