Herpes zoster associated with the Oka vaccine strain has been documented in 23 vaccinees; another 15 turned out to have wild-type virus
Secondly, opportunities for mutational change may occur when the virus is able to circulate between the gastrointestinal tracts of susceptible persons in populations where the wild-type virus
has been eliminated but vaccination rates have fallen, resulting in populations highly susceptible to infection.
determination of IC50 for the patient's isolate and the wild-type virus
Results suggest that HIV that is resistant to some drugs, especially 3TC and the protease inhibitors, does not replicate as well as wild-type virus
In this case series, some patients conserved the resistant viral population after antiviral pressure removal, whereas another patient (patient 1) cleared his resistant viral population to recover a fully wild-type virus
Genotyping showed that the patient taking raltegravir had wild-type virus
, whereas the patient taking efavirenz had resistance mutations consistent with exposure to that drug.
Reports of outbreaks of mild cases of chickenpox among immunized children in child care centers led to studies showing that breakthrough cases of disease after vaccination occur in about 15% of children exposed to the wild-type virus
, although breakthrough disease usually produces fewer than 50 lesions; is less severe; and, generally, is half as contagious as natural chickenpox.
33) Though 64% of patients in the STI group experienced a shift to wild-type virus
by 4 months, there were significantly more cases of disease progression in the STI group, compared to the control group.
The risk for congenital varicella syndrome after natural infection with wild varicella zoster virus is 1%-2%; because the virulence of the attenuated virus used in the vaccine is less than that of the wild-type virus
, the risk to the fetus, if any, should be lower (1).
The article points out the possibility of recombination between a vaccine strain and a wild-type virus
, which would result in a new, potentially dangerous virus.
In particular, C6 and P29 mutants were rapidly outcompeted by a wild-type strain in the absence of antibodies, and although they were able to overcome the wild-type virus
in the presence of the K34C8 MAb, it was only after a slow process (Figure 2), indeed indicating a very low fitness.
During this testing period, wild-type varicella was present in the community and children either came down with the disease or were boosted from exposure to wild-type virus
if they had participated in one of the vaccine's many clinical trials before the vaccine was licensed.