Ricin chain A. This vaccination is effective for several months due to the body's production of antibodies to the foreign protein. In 1978 Bulgarian defector Vladimir Kostov survived a ricin attack similar to the one on Georgi Markov, probably due to his body's production of antibodies. When a ricin-laced pellet was removed from the small of his back it was found that some of the original wax coating was still attached. For this reason only small amounts of ricin had leaked out of the pellet, producing some symptoms but allowing his body to develop immunity to further poisoning. The seeds of
London Buses route 7 from Wormwood Scrubs were renumbered 7A. This situation remained until 3 October 1934, when the newly constituted London Passenger Transport Board instituted its own numbering system. Route 7 continued with an extension to Kew Green until 22 August 1946, when the 7A was revived from Acton to London Bridge. Route 7 was withdrawn on 19 August 1958. From 14 October 1959, the old route 7A had its suffix removed, becoming plain 7. The service ran between Acton tram depot and London Bridge station via East Acton, Ladbroke Grove, Paddington station, Edgware Road, Marble Arch, Oxford Street, Holborn station and Bank