I'm actually a geneticist and have been actively keeping up with the research that has been published and want to help fellow pedes get the upper edge over the traitors in terms of information. So, the recombinant DNA which you have mentioned are when segments of the viral genome are recombined with a plasmid (single stand of DNA) and used as a vector into a person. So in relation with the COVID vaccine, certain regions of the viral DNA that cause the disease are removed more preferably the E1 and E3 region and due to this even when you get the vaccine you won't have the actual active disease causing part of the DNA. However, all the remaining proteins and the promoter regions that are present are still coded for by the recombinant DNA; this means that when it enters your cells you body is able to use that DNA to produce the proteins that are encoded which is mainly the antigens of COVID-19 so that there is an immune response so antibody and memory B cell production can occur without coding the disease and thus giving you immunity. Moreover, the MRC-5 cells that you are talking about MRC-5 cell that you were talking about were mainly used to see how this vaccine would affect human lung tissue as COVID-19 is a respiratory disease and none of the MRC-5, A549 and HEK293 cells that are all types of lung epithelial cells were used actually in the development of the vaccine and this was confirmed by Pfizer, Oxford and Moderna. I would also like to take this opportunity to point out that althought these cells were originially acquired from an aborted foetus in the 60s and 70s it has seen been regularly grown in the lab so they are not taken from a freshly aborted foetus. I've attached the paper that shows how MRC-5 cells were used to explore the expression of COVD-19 when using the vaccine candidate.
https://assets.researchsquare.com/files/rs-94837/v1/bb7a369c-a69d-460e-be49-e0ecc3cd3e93.pdf
The bovine serum isn't actually drawn from the beating heart of a cow foetus but is actually sold by suppliers who use the foetal blood when a pregnant cow is killed for their meat at bucheries. Hence why it is quite expensive and you can even get cell strain manufactured bovine serum.
https://www.thermofisher.com/uk/en/home/life-science/cell-culture/mammalian-cell-culture/fbs.html?gclid=EAIaIQobChMIuM6__cXz7QIVD5ntCh3nBwehEAAYASAAEgJvrfD_BwE&ef_id=EAIaIQobChMIuM6__cXz7QIVD5ntCh3nBwehEAAYASAAEgJvrfD_BwE:G:s&s_kwcid=AL!3652!3!414347351731!p!!g!!foetal%20bovine%20serum&cid=bid_clb_fbs_r01_co_cp0000_pjt0000_bid00000_0se_gaw_nt_pur_con