Intramuscular injections within 30 days of immunization with oral poliovirus vaccine - a risk factor for vaccine-associated paralytic poliomyelitis. 1995, Strebel, N Engl J Med

Between 1970 and 1984, Romania participated in tests of the safety of oral vaccine under the auspices of WHO, it turned out that in Romania, for some reason, 5-17 times more cases of vaccine-associated poliomyelitis (VAPP) are registered than in 12 other countries At first thought that in Romania the vaccine was too virulent, but in 1990 it was replaced with another vaccine, but the frequency of VAPP did not change.
There were 31 such cases among children from 1988 to 1992. Of these, 18 had a vaccination paralysis, and 13 got infected from vaccinated. They were compared to non-paralyzed children. It turned out that 87% of paralyzed children received intramuscular injections 30 days before the onset of paralysis (an average of 16.8 injections each), compared with 51% of non-paralyzed children (an average of 2.8 injections each). Each injection increased the risk of paralysis by 13%. In those who received one injection, paralysis was observed 8 times more often than those who did not receive injections, and those who received more than 10 injections, paralysis was observed 182 times more often. Penicillin injections increased the risk of paralysis by 62 times, injections of other antibiotics 40 times, and the DTP shot increased the risk of paralysis by a factor of 3.
86% of cases of VAPP were caused by injections. If children were not injected 30 days after OPV, the average number of cases of VAPP would not be 10.3 per year (1: 178 thousand), but 1.4 per year (1: 1.3 million).