New Vaccine Strategies

Nerem and colleagues also devised a number of plans to stretch tight vaccine supplies to see what might work.

But first, the clinic decided it had to protect the overall integrity of the Pipestone System. That meant reserving a small quantity of full-dose vaccine for incoming breeding stock, particularly the 21-day-old replacement gilts purchased, and for limited use in sows as a pre-farrowing vaccine trial.

“We did a limited trial in sows because we knew there was a product that was labeled for use in sows in Europe (Merial), and we wanted to see if it could make a difference in maximizing use of the vaccine,” Nerem explains.

PCV2 vaccine was administered to about 18,000 sows from November 2006 through January 2007. No measurable changes were observed in sow and litter performance as measured by standard PigChamp data analysis. Most pigs from vaccinated sows were vaccinated in the nursery, so offspring performance from vaccinated sows could not be measured. Another confounding factor was an outbreak of PRRS that struck some sow units in January 2007, he notes.

The bulk of limited vaccine supplies went to commercial wean-to-finish systems using three guidelines:

• Vaccinate affected flows or sites only;

• Vaccinate pigs 3-6 weeks of age; and

• Vaccinate pigs with ½ dose of commercial vaccine.

By the spring of 2007, vaccine demand had drastically outpaced supply. The Pipestone clinic implemented a focused plan to make the most of vaccine supplies:

• Vaccinate affected flows or sites only;

• Vaccinate pigs at weaning at the sow farm; and

• Vaccinate pigs with ¼ dose of commercial vaccine.

As vaccine supplies increased this summer, but were still not enough to use full-dose vaccine throughout the Pipestone System, the strategy became:

• Vaccinate affected flows or sites only;

• Vaccinate pigs at processing and at weaning on the sow farm using the two-dose product; and

• Vaccinate pigs with ½ dose of commercial vaccine.

Nerem told the crowd at the Leman Swine Conference in St. Paul, MN, that he understands those vaccine strategies didn't follow the label guidelines developed by the manufacturers.

“I am in no way advocating that kind of use. We had a very tough decision to make. We made a decision that there might be another way to reduce shareholders' risk, and prevent disease in young pigs, by using less than a full dose of vaccine,” he explains.

Trial Conclusions

The main objective of the partial- dosing protocols was to maximize the number of pigs getting at least some protection, Nerem emphasizes. He summarized those results:

• Pigs given ½ dose of circovirus vaccine from 3-6 weeks postweaning performed very well. On several occasions, vaccinated and unvaccinated pigs from the same source were placed on the same finishing sites. For roughly 10,000 pigs compared, vaccinated pig groups closed out with 2.7-5.0% mortality, while unvaccinated counterparts finished with 11.4-23.7% mortality. He says clinical signs in most vaccinated groups were minimal to non-existent.

• Pigs given ¼ dose of circovirus vaccine at weaning were closing out at the time of his presentation in mid-September. But Nerem says preliminary data clearly indicates that most groups getting ¼ dose of vaccine lacked complete protection, with mortality and prevalence of clinically affected pigs both running higher.

• In another limited trial, pigs were given ½ dose of commercial vaccine twice preweaning. Results were not available at presstime.

Overall, using ½ dose of vaccine has provided acceptable results when given to pigs at the appropriate age (under 6 weeks of age), says Nerem.

Current Program

Now that it appears sufficient quantities of PCV2 vaccine are available, the Pipestone clinic will use vaccine at the full dose recommended by the manufacturers on the label.

Nerem observes: “Our shareholders now expect to get vaccinated pigs when they receive them from the sow farm. So we have implemented a program of delivering vaccine to the sow farm for use at piglet processing and at weaning (two-dose program). We are seeing good results from that strategy, and those pigs are just coming to market now.”

He stresses again, even though it is not the manufacturers' recommendations, the Pipestone clinic has been able to immunize pigs prior to weaning and get protection to market. Circovirus vaccines are federally licensed for use in pigs at 3 weeks of age and older.

Finally, the clinic is conducting an experiment to investigate the return to growth performance from vaccinating pigs with a full dose vs. a half dose of vaccine.

“Certainly, the mortality data would indicate that the results are very similar with both dose regimens, but there are probably some advantages to a full dose of vaccine, and we are seeking to verify those claims,” Nerem points out.

The jury is also still out on sow vaccination. He admits more work needs to be done to determine the impact on maternal antibody as well as the piglet vaccination program.